B. linens needs a high pH (usually 5.8 or higher), moisture and salt (one of the very few bacteria that requires salt).
When you are washing, make sure that you are using a light brine. Typically 3 or 5% is the strength. Higher than that inhibits yeasts. You need the yeasts because that's the principle way that the rind will get to a high pH. The more yeast you have growing on the rind the faster b. linens will show up. Keeping the temp up can help quite a lot too. Even 15 or 16 C can be quite good.
Washing each side every other day, and pulling up a bit of paste into a schmear is the classic way to do alpines. Using a very soft brush and really scrubbing the rind so that you get a beige paste is what you want to do. Here is *the thread* for alpine rinds:
https://cheeseforum.org/forum/index.php/topic,10633.0.html Alpkäserei is a pro who makes alpine style cheeses and is *very* experienced with that style. On the third page you can see him washing his cheeses. There is also a good picture of what a schmear should look like near the bottom (posted by Al Lewis). At first, you'll just be pulling up beige paste and over time it will get darker and darker (red, pink, orange, brown and beige are all possibilities though). You will be able to tell by the smell :-)
I've found recently that the sides of my cheeses are drying out faster than the faces and I think it's important to start washing before that happens. The schmear holds the moisture in, but if you let it dry out, it's really hard to get the schmear going. The result is that I have good b. linens growth on the faces, but not the sides. YMMV.