Well I find it really helps to not try to do everything on your own, even if it's just using drawing references occasionally. Books can be a good substitute for lack of classes. For me some of the most helpful things have been the Hogarth
series, maybe he should have been on my list now that I think about it. I don't read his actual comics but I study his work.
Man he has a Dynamic Wrinkles and Drapery, I'm not entirely sure what that is but I want it.
I only own the Dynamic Figure and Hands books, which I need to study more but even the little I have done has improved my work allot.
EDIT: As I thought, the Wrinkles and Drapery is entire book on detailing clothing on people. I totally want that.