Hey i didn't say it looked good.
Also how do i put on riviets and wear and tear on the plane?
For rivets you'll want to make a brush that's one pixel with a space of like 3-5 px in between each replication (I guess is what they call it?) when you shift+click. You can find the tutorial for making brushes on GIMP.org, they're great tutorials.
As far as weathering... come up with something. That's the fun

Everybody has their own techniques for this kind of thing, and they usually vary by plane.
My biggest suggestion on the latter issue is to study pictures. I think I looked at pictures/ read for about a month before I started my Dora template, which I'm currently working on. Even now I've still only done MOST of the shadowing/panel differences (I have 6 different panel opacities in this template).