I've seen where other people have scanned drawings and they came out great! Whenever I've tried that, there was too much to clean up! I make a lot of lines because I sketch as opposed to line draw.
The technique I'm using now is to create a sketch using my new Bamboo digital tablet. Then create a layer over it and carefully trace only the lines that I want. Then I fill it with color and texture and remove some of the outlines. Tedious, time-consuming, and after awhile very boring, but it gets the job done.
I'm now looking at 3D modeling programs, but I'm so busy with projects that I haven't had time to try any out lately.
btw, your avatar makes me dizzy!