K... I think you understand what the muscles are, but you're not completely in full understanding of how they're all formed. This is important, and this is what's holding you back. So let me link you to a post I made about pectorals a while ago: http://www.polycount.com/forum/showpost.php?p=1946653&postcount=54 It looks…
3DCoat can be a good solution for painting stylized textures. You could also give a look into Affinity Photo. https://vimeo.com/194672406 I use Affinity Photo to quickly turn Vectorshapes, Brush strokes or Text on curves into Normal/Height maps for further usage in Substance Painter.