Sketch coloring is good, because it gives me a better view of what the finished image will look like.On a new layer set to multiply (or gel in Painter), I paint the various colors I want, not worrying about edges that much for now. On another layer on top of this one (set to normal) I paint with a 50% opacity brush in black and white, highlighting and shading based on the direction of my light source (in this case the sun, "off camera").I colored this sketch both in Painter and PS, can't really recall the exact brushes used because I was just experimenting.