Just experimenting a bit with Photoshop again (pay no attention to the fact that the rock is pretty damn weird and oddly lit, this was a quick test). I'm kind of happy with the result, even though it's got that ugly effect where you can clearly see all the brush strokes. This is never a problem with SAI because the brushes blend with the colors on the canvas, but if I'm able to find a way to hide this better, I might start using Photoshop instead...
EDIT: Oops, and the image is gone because I was cleaning out my Dropbox and I accidentally cleaned too much. >_> Nevermind, it wasn't much to look at.