Thanks! I've been working with the opacity on the layers a bit, but the blending one still confuses me a bit, so I haven't been working with that as much.

I follow the icon-tutorial community! They aren't very active lately and seem to mostly post PhotoShop things, but I figure it's still informative. Thanks for the link, it was actually useful! I'd been wondering what exactly the mask layer was!

Yeah, I have an undo button, I just wish it would list my actions. I'm pretty sure GIMP does. I don't think you can randomly undo something in the middle, but sometimes I just want to see the last couple things I did so that I can figure out what caused the problem/effect or whatever.