I'm a bit late to the game, but I had an old QFR laying around and I felt creative this weekend.
I'm a total noob at this. As you can see, I wasn't very concerned with the inner surfaces. The paint process was basic: Sand, a couple coats of Valspar plastic primer, several coats of Valspar gloss-white lacquer, and a couple coats of Valspar lacquer clear-coat. I lightly sanded with 800-grit between coats. I was going for a sheer gloss look, but as you'll see I ended up with something else.
After discovering how hard it was to get that rubber off, I ignored earlier tips and went at it with 60-grit. As a result, I scratched the case up a bit. But the scratch lines combined with the lacquer paint make it look and feel a bit like painted wood. I like it.
With black keys for maximum contrast. These are WASD's new UV printed keys. The texture works well with the paint.
Now we see the magic. The lacquer paint produced a wonderful texture!
Close-up of the texture.
And now the science! Below this new case lurks... a monstrosity. Last year, I decided I needed Colemak in hardware. The WASDv2 wasn't out yet. I did what I had to do. I am not proud of this work. (I am, however, happy with the results!)