You're in luck, because I haaaaave - a step-by-step GIF for a Grassblades-page! (You might have to click on it for it to actually work)
Briefly, in words - after I'm done inking (figures and backgrounds on two different layers), I lay down the flats (also on two different layers - it's easier to correct stuff that way), and then do 90% of my shading on a multiply-layer, and then I adjust the lighting with overlay/glow-dodge. This
particular page contains more actual shading on the flats-layer than I usually do, as it has water on it, and water is a complex thing to colour. But that's the basic process.
Multiply, overlay and glow-dodge are my best friends in colouring.