That's an interesting question. I didn't think that my sketches were good enough to just color on. They are kinda sloppy! How would I go about doing that?
well, you'd need to keep some of the mess, so if you're going for a straight cel shaded cartoon-look *which i assume* there needs to be a balance.
try bringing up the contrast and brightness from your sketches and working and cleaning up from that.
if that won't work and you can't get the lines clean enough for the look you want and you still need to overlay digitally, then try more varied line, *i don't think i explained that right* a line that is thicker at the start and thins out or breaks, instead of one that stays the same width. that might help keep it from flattening out (heavier, darker lines visually fall behind thinner, lighter lines, creating depth) and retain some of the motion and keep the clean look.
http://www.viistar.com/images/2d/manga/ ... eux6_0.jpg
probably isn't a great example for what you want, but it shows the varied lines i was talking about. for me, i transfer from a sketch to inking paper with cotton drafting paper, and then scan. i feel more in control of the lines working by hand (seeing that i lack a tablet)