Here's a figure drawing and muscle/form analysis. I'm starting to feel more confident with placing muscles on the figure, especially in the forearm, I think I'm finally figuring out how to orient it properly so the muscles can be figure out. The secret is in the ulnar furrow, which is the line of the ulna from elbow to little finger that's subcutaneous and separates the flexors and extensors. If you know where that is, it's easy to figure out where the flexors, extensors, and supinators should go, which makes forearms pretty simple.
Still gotta work on getting the forms down solidly though, Dean Cornwell's charcoal studies are great to look at for that, he was a master of form wedging for sure.
Thanks to justmeina on dA for the great reference!