Thanks for the awesome comment .
Do you mean the Stampleton study? I used pretty much the same technique he used in his video so be sure to check that out.
My actual painting method is very similar if only more 'organic'.
I avoid using many layers or fancy brush modes. I believe that painting everything yourself forces you to have a better understanding of what's going on and why colors are the way they are.
Here's how i usually start. I draw my lineart and then i open a new layer underneath adding some flat colors.
So far i'm doing exactly what Stampleton did in his video.
I then proceed to add some cast shadows.
Then the fun part begins. I start rendering trying to define the forms. I try to do most of it 'manualy' using a version of Marc's square brush. However i do use the smudge tool here and there.
Lastly i'll use a bit of overlay and multiply to saturate,lighten or darken certain areas of my characters.
Hope that helps so far. If you have any further questions i'll be more than happy to provide more info