Ah, that's pretty neat! I did something similar before I got a drawing tablet, but I'm starting to rethink that idea. I've always found the draw/ink/scan gave you more flexibility in art.
My issue with that strategy is that sometimes the black outlines always end up with those annoying extra pixels when you fill color you can just make out the tiny white pixels. I'll have to play with it some more so I can get a better formula down.