Since a few people have asked how I do my paint horses and appaloosas....
And because I've given away so many characters that I know are daunting to draw.
Presenting my most awesome tutorial. This was made in Photoshop, but GIMP and Paint Shop Pro (and I'm fairly certain Corel) follow exactly the same logic; just a different layout is all.
Also for the selection, you can just draw randomly all over the place and then (at least on GIMP) go to Select (up top) > Distort and then adjust the settings to whatever fits your work best (lot of trial and error) and that works as well.
I don't use GIMP myself, but I've heard it has all the basic features of photoshop. Layers and the lasso tool/selection tool/magic wand tool are very basic features, and GIMP should have them, they might just have a different name or symbol, so you'll just have to search for them. But once you've found the correct tools you can follow this tutorial without any problems (a lot of my watchers are GIMP users, and they all follow my tutorials without a problem)