But if you look at the picture, you can see that the fragmentation is far, far too small and unorganized to have been done with a brush. A sponge, maybe, but drybrushing doesn't work like that.
It seems like the salt use is the most likely culprit (on the Valdor I mean); however, I have my doubts as you can also see fragments of the camo colour over the base colour, which would mean the painter painted a base of opposite colour at each site where he intended to put (and not put) the camo. This seems quite unlikely.
Still, I think I'll use the salt method. It seems to work very well. On the subject of removing solids from models; has anyone tried using masking fluid? I have some of that as well and with that you could also potentially achieve the effect of solid texture around the area of fragmentation, quite easily.