Hey, thanks a ton!
Here you can see I've begun blocking out the coloring.
I'm gonna be using 6 different layers, the hard shapes are selected using lasso tool.
1 - line art (on top)
2 - skin (all of it)
3 - everything else on the girl (hat, clothing, hair, etc.)
4 - yellow robot panels
5 - everything else (stuff on the floor, robo-guts, etc.)
6 - background (solid color for now)
I just lock the layers I want to work on and paint everything in one-layer, No gradient maps, no greyscale to color nonsense, no screen/multiply/overlay bullshit. Everything on one layer gives you a much more natural looking result, and absolute control over a piece. If you need a few more layers for some effects, use clipping masks. This process is significantly faster than any other method because you do not have to navigate many layers, however you need to properly understand color, light, value, and bringing all of it together. No training wheels on this bicycle!
I've got the skin already mostly done, a basic block out of hard and soft edges for the shadows. I'll eventually clean it up and polish everything, but for the time being it works and allows me to make sure the piece is gonna be fine. I tend to block everything out first, color adjust, then do a final polish pass.