Let's start with a quick bit of colouring. Image borrowed from Inktank.com
I like the idea of colouring on a computer, because if you don't like it you can do it again. It's a lot easier to do various effects - a number of which can be changed after the fact.
There's also a few tricks you can do - like Multiply Layer - to let you work fast and (gasp!) sloppy and still have it look nice.
Might have to adjust your tool's presets though: