For blue, you problem is likely the daily brine washes. Natural rinds are tricky to learn how to do because the goals are counter intuitive. We tend to want to create a "clean" rind, but in attempting that we create an environment that only blue mold will grown on. There is a book on agriculture called the "One Straw Revolution" where the author creates a hypothesis that when you intervene in a natural process you take on a lot more than you bargain for. The natural processes are *very* complex and you need to account for every detail if you do that. He thought that it might be cheaper and easier to try to co-opt the existing natural processes to achieve his goals rather than intervening directly. I feel the same way about natural rinds.
Almost nothing grows on a young cheese rind. We can see that easily at the start. Nothing grows for a few days (or even a week). That's because the environment is actually pretty hostile to mold -- low pH, high salt and the only food is lactate. Over time the cheese absorbs the salt. The enzymes from the starter culture break down the proteins. Yeast starts to grow on the outside of the cheese and it pulls the pH up (makes it less acidic). This allows more and more things to grow on the rind. But even still, at the beginning the main things that can grow are blue mold, geotrichum candidum, penicillium candidum and a few other yeasts (geotrichum is technically a yeast, though it's kind of half way between a mold and a yeast).
We don't want blue mold to grow. However, of the things that can grow on your cheese, it has the most salt tolerance: 8%. Geotrichum can only tolerate 3%. If you wash your cheese with brine, you will kill everything and then blue mold will grow. If you wash it again, you will kill everything and then blue mold will grow. The more you wash the cheese, the more you are selecting for blue mold. After you've washed it 3-4 times, *only blue mold will grow*. You have already experienced that :-) Some people will wash with vinegar, or alcohol, but you end up in the same place. You decrease the pH of the rind and now you need to wait for the yeasts to show up and grow on your rind to reduce the pH and then you start all over again. Blue mold shows up and you wash it and then you select for blue mold again. You end up extending the "young" period of your cheese indefinitely and it never establishes a rind.
Instead of battling blue, what we want to do is to encourage other things to grow. If they outcompete the blue, then there is nothing we need to do. The more we try to intervene, the more details we have to control. But if we leave it to nature to take care of it for us, then there is almost nothing we need to do. Our key ally is geotrichum candidum in most cheeses. If you are doing a bloomy rind with penicillium candidum, then that's your ally. But honestly, once it gets established you don't have to do anything because it's an absolute beast. I've got a Camembert style that got some blue on it and I just laughed, "Do you think you have a chance against PC? You are so naive!" And I left it alone. The blue is a memory now.
There are a couple of things to understand. Geotrichum enjoys large, flat, smooth surfaces. Blue likes bumpy, craggy surfaces. So our first line of defense is in the make. When you press your cheese make sure there are *no* marks on the cheese. I take 2 hours to drain the cheese and try to close the rind at the end of the second hour. For the last 30 minutes of pressing, I remove the cheese cloth. After that, I "depress" the cheese. That means leaving it in the mold and turning it just so that any marks are erased. For some cheeses I might do a very light pressing if there happens to be a lot of stipples from the holes in the mold, etc. The smoother the surface of your cheese, the easier time you will have.
Next, you want to cultivate geotrichum. Blue likes cold, humid environments. Geotrichum likes relatively dry environments and a temperature of about 16 C. If possible, after drying the cheese, I try to find a place to leave it for a day or two where it can pick up yeast. If you have an other cheese that already has geo growing on it, you can wipe that cheese with a cloth and then wipe the cloth on your new cheese. Job done :-) Also, I tend to use bamboo sushi mats as draining mats in my boxes. If I have an old cheese that's aging well, I'll use the mat from that cheese for the new cheese and put the new mat under the old cheese. That kind of thing. But if I'm starting from scratch and I have no cheeses, I'll up the temperature of my cave to 16 C and let it age for the first few days like that.
You need to keep your cheese dry to the touch. If it is wet, then Geo is unhappy. You can often see beige gunk on the suface of your cheese and the cheese will be slimy. That's geo (and other yeasts). They will draw moisture from the cheese itself, so you need to keep the humidity down. If it's really bad, geo will build up in a thick gunk and even grow bubbles. If you pop the bubbles, you'll find geo blooming inside! If that happens you need to wipe it *all* off and thoroughly dry the cheese. That gunked up rind will never do anything you want.
Humidity control is very important. You have a couple of controls. First is the size of your maturation box. The bigger the box, the less humid the air. It's kind of intuitive. No box means the lowest possible humidity. If you wrapped it in cling film, it would have the highest possible humidity. The rule of thumb is that your box should be 3 times the size of your cheese. For every 500g of cheese you need 1.5L of space (for every 1 lb, you need 3 quarts of space). I tend to go just a tad bigger (because that's the only boxes I could find) at 1.7 liters per 500g and it tends to be OK.
The second control is temperature. The lower the temperature, the higher the humidity. Humidity is measured in "relative humidity". It's the ratio of the amount of water the air is holding to the amount it *could* hold. Warm air can hold more water than cool air. If you warm the air, the air can hold more water, but the amount of water in the air doesn't change. This means that the relative humidity goes down. If you cool the air the air can hold less water, but the amount of water in the air doesn't change. This means that the relative humidity goes up. If you flip your cheeses in warm air and then put them in the fridge, you will usually have higher humidity than if you flip your cheese in cool air, because the air where you flipped the cheese had more water in it. It takes a while to get used to the idea...
Anyway, if your humidity is too high (the cheeses are wet), then increasing the temperature will reduce the humidity. If your humidity is too low (the cheeses are cracking), then decreasing the temperature will increase the humidity. Also realise that fluctuating temperature can cause it to "rain" on your cheeses. For example, if you put your cheese in the cave at 13 C with a relative humidity of 85%, if it goes down to 6 C over night, the humidity can easily get to 100%, which will mean that you get dew on your cheeses. Even when it warms up later, the humidity in the air has gone down, but your cheese is covered with water (I've been struggling with that this winter).
You can stick a paper towel in your boxes to absorb some water and replace it every day, but the main way to reduce the humidity is to get a bigger box, increase the temperature, and to ensure you have an even temperature (even trying to find a cool place to flip your cheeses will help). Also consider that there are 2 water sources in your maturation box: the air and your cheese. You need to wipe out your box *every single day* so that it is bone dry. Failing to do that even one day will cause the humidity to spike. That's because water is coming out of your cheese all the time as it slowly matures and dries. The biological action of the mold also releases water into the air. Just keep wiping it out. But also consider that you cheese might just be too moist. 80% of aging the cheese is making a cheese that can be aged. If your cheese is too moist, give up and make another cheese :-)
If you are battling humidity, and your cheese is wet, tacky, sticky, slimy, then dry it off with paper towels and let it sit outside of the cave for a few hours until it dries off. Then stick it back in. Keep doing that every day until the cheese is dry to the touch. Sometimes you have to battle a long time with that. But remember our goal here is to favor geotrichum, that likes that dry smooth surface.
When you first start aging your cheese, and before your cave has really gotten established, you'll that blue always shows up because it can handle the salt on the rind. There is another nice thing in our battle between blue and geo. Geo *digs into the rind*. If forms roots and alters the surface of the rind. For some variants, you can see that brainy surface. For others it's small enough that you need a microscope to see it. But it always does that. Blue, on the other hand, tends to grow on the surface and hang on to the cracks and crags. If you brush the rind off, you will favor geo over blue. That's because even fairly vigorous brushing won't dislodge the geo, but it will dislodge the blue.
Apart from environment, brushing is your first line of defence. You want a soft brush with a stiff bristle. Horse hair is traditionally used because it has a hook at the end that cleans out crevices on the cheese. However, something similar to a shaving brush is what you want. I actually use a surgical nail brush (the kind that doctors use to clean underneath their fingernails). A baby's tooth brush or an old shaving brush would be fine, though, I think. You can also use a cloth, but it doesn't work quite as well. Basically you want something that will clean off the the mold, but won't score the rind.
Just brush off the anything blue every day. Leave anything white.
You can wash the rind once or twice, but you should only use a 3% w/v brine -- 3 grams of salt in 100 ml of water. That's the maximum that geotrichum can tolerate. Even if everything is under control, sometimes it's useful to wash it once in the second week to spread the geo. You defintiely do *not* want to wash it every day because you will build up salt on the surface and you will also keep the cheese way too wet.
The other problem with washing is that as the yeasts (and geo) grow, the pH of the rind goes up. Once it gets to a pH of 5.8, brevibacterium linens can grow. It only grows in a high humidity environment. If you wash the rind after the pH has reached that level, b. linens *will* grow. That's fine if you are intending to do a washed rind, but bad if you aren't. For a tomme, you might want to intentionally wash once at around week 4 and take everything off. B. linens will grow, but if you keep the humidity down after that, it will just add complexity to the rind. The succession molds will start growing on top and you will have a very pretty and interesting cheese. But if your humidity is too high, you may end up with a mess. I consider it an advanced technique. YMMV.
And that's about it. I always say that aging natural rind cheeses is a skill that's at least as deep as making the cheese in the first place. Also, like I said, 80% of aging is in making a cheese that will age the way you want. I recommend planning to eat your first 20 or so cheeses early and building up your skills so that aging is easy for you. Trying to force your cheeses to age almost never goes well. Fresh cheeses are delicious, even if they aren't so complex. Aged cheeses that have gone wrong are almost never delicious. You can do what you want, but since you have caught the cheese making bug, I advice is just to relax and keep making lots of cheese. Eventually again will click for you and you will wonder why you ever though it was difficult.
