GIMP 2 Review

Okay, I think I need to take some digital graphics classes because I don't have a clue how to use a program like this. I know what I want to turn the picture into, I just don't know how to create brushes to get it to look the way I want. I've downloaded brushes that were already made, but all of the ones I like and need are for photo shop.

Here is a picture I made last night, it took me a very long time to figure out how to use everything:

What is wrong with this is the lines are horizontal, not diagonal. Also the corner's are supposed to be rounded, but I couldn't figure that out either. All of this stuff is probably very very simple, but there aren't a lot of specifics about making certain things.  Another problem is there are directions online about how to make things, and they tell you where to go to find them, but when you look for them in the place they are supposed to be, they aren't there.

I would probably love this program if I could figure out how to use it properly.