Making a simple grunge texture

I got bored this weekend and made a tutorial
This is how I make simple grunge texture without needing go through stock pictures.
I'm not saying, 'stop using stock pictures', but I'm more less saying that if want to make your own, you can, since G.I.M.P (2.2) is slightly more limited then photoshop, it isn't always easy to get the same quality.
So, yes it's just a simple basic idea, I wasn't sure if this is what you exactly call 'grunge', but I wasn't sure what else you could call it.

I haven't done a proper tutorial on dA before, so sorry if it isn't that good. I thought to put in the real basics in this, since I know people that don't even know what a layer is, let alone how to get a new one.

I'm not sure if this has already been done on dA ~ but oh well, it ish done now

Part 2:[link]

The pictures of tree (with the effects): [link]

Notes:
G.I.M.P 2.2 image @ [link]
Tutorial (C) T.D.O.W
Tree Photo (C) T.D.O.W