The last time I did one of these I felt it was inadequate because all I did was flip through the layers of a completed piece. So this time I took screenshots as I drew!
This is only my method for fast colouring; if I had, say, metallic objects, or fur to colour I would likely paint it with none of the shadows layer masking business, which seems to work best on objects that aren’t particularly shiny.
If you look at the timestamps, apparently I took about an hour an a half to colour this.
Smoothing out the shadows was done with a hard round brush with flow and opacity controls turned on. (it’s a default brush.)
Your flat colours are the most important part of this process - the layer adjustments trick will save you from having to pick a second round of colours for shadows manually, but if your flats aren’t up to scratch the whole piece will suffer. Make sure your colour scheme works here before moving to shading.
Finished product can be found here. I hope this is helpful!