Well, adding to curds before pressing certainly is a direct method of salting
- but no, I was referring to putting salt on the surface of a cheese after it has been pressed and removed from the mold.
Generally I put about 1/4 of the salt on the top of the cheese and put it in the cave or refrigerator to cool - this will help to slow further development of acid while the salt works its way in. Then around 12 hours later - i.e., that evening if I started in the morning, or the next morning if I started in the evening - I flip it over and put 1/4 of the salt on the other side. Note that, especially if you are using kosher salt (which I find works better than finer salt for this purpose), there will still be salt crystals visible on the surface; I flip the cheese carefully to retain and "trap" those crystals on what is now the bottom, and add the new salt to what is now the top. Continue this twice more. (When I flip it over the second time, the salt crystals that were on the bottom have disappeared/been absorbed.) This will draw out some whey as the salt works its way in, so you get a little bit of a mini-brine working on the bottom of the cheese at the same time. (Use a tray or a plate that has enough of a "lip" to it to contain this "brine.") After the final salting, I generally flip one more time, wait another 12 hours - this lets the salt crystals that were left on top join the developed brine to continue to work - and then dry it off and move it to the cave.
Note that you can also start out with salt on both sides - use 1/4 of the salt on top, place your tray or plate on top and hold the cheese and plate together as you flip it over - now that salt is trapped on the bottom, and you can add 1/4 of the salt to what is now the top. Note also that with the direct salting method, "12 hours" is very flexible - part of the appeal of doing it this way vs. brining, where an hour or two can make a big difference!
It may require a bit of experimentation to get the right amount of salt to use when doing it this way, but as a rough rule of thumb, I find that 3 Tbs of kosher salt is a good amount to use with a ~4 gallon make -- depending, of course, on what the final goal/type of cheese is. (For example, I use only about half that much with a swiss make.) You can certainly weigh the cheese and weigh the salt to calculate a target percentage, but you have to keep in mind that not
all the salt will be absorbed; some of it will be lost in the "mini-brine" that develops. I generally just work by Tbs. or tsp. measurements, with past experience as a guide.