That sounds good, thanks for the tip. I think I might have to stock up on soot powder later since I don't have it available within buying distance.
Instead, I went to the campus store and got black fountain pen ink, which I thinned down and then soaked the lichens twice. Now they are decently black but still have a bit of a color variation, which I like. They also got stiffened through the last ink coating. I think I might drybrush them a little with a lighter grey once they are mounted on the bases
The ink I used, it cost about $5.00
After soaking with 1:8 thinned ink
After drying of a second soaking with 1:4 thinned ink and drying over night, with, and without flash.