I might have just figured out how to color muscle groups!
Oh my god, I feel like having made lots of progress drawing this one. I usually avoid coloring bare skin because it's so hard to make it look right. But today... I don't know what got into me! But I guess the most important thing is that you have to know the basic shapes of muscle groups, and how they connect and overlap. One week's figure drawing practice paid off I'm so happy!!!
BUT, after I finished the whole pic I found that some parts are not as pronounced as I wanted them to be, and it's hard to get that effect without major changes (and from my experience even if I try I will probably end in more frustration only...), so I decided to leave it, and maybe look at it again tomorrow.
I hope I can draw a couple more before deadline. My art hasn't got to the fun parts of the fic yet.