I learned a few things this challenge, I think the more important (most) importatnt thing I learned was not to rush anything. Like, its easy to just want to be finished with a piece, and sometimes you just have to know when to quit, otherwise I'd say work on it until its finished.
I also learned that I"m not quite confident with colors yet haha. I tend to simply put a multiply layer over them. I'll focus on that after I get lighting down pat, which hasnt been done yet. So color wont be coming any time soon haha.
I also learned to start from a fairly "realistic" drawing, before I cartoonisize it. (a word I believe I made up just now). In addition to that, this is for future Paul, but be more confident in your strokes, you ,know what you're doing. And dont be so hard on yourself the first few thumbnails will never be that good unless you're a genius or something.
IF you're going to detail one part of the picture, do the whole damn picture, not just half, it looks bad.
Thats all I can think of at 4:30 in the morning, I woke up an hour ago, and I've got to get ready for work.