I don't think I should be in that list of names, but thanks.
Only just saw this. Haven't checked forums since early Saturday.
Random thoughts:
If it looks like a repeating pattern, it is a repeating pattern, and you need to do something else. Meaning the stamp-like brush shapes are a dead givaway. Avoid them if you can.
Use a LOT of layers. If you've got a wing underside, and you're putting oil stains, gas stains, gunsmoke stains, paint chips, dirt streaks, and paint fading, put them ALL on their own layer. If the time comes when you want to change any one without affecting the others, you're porked.
Overdo it. No, seriously. What you see on the bitmap often is barely visible in-game. You can start by eyeballing it in the editing software, but then go in-game and zoom out a bit and objectively say to yourself "Does it look like there's anything on there?" -- often the answer for me is "no" -- so go in and up whatever you've done 20%-25%. Check again in-game. Often you've gone overboard (and sometimes you find you've hit it on the nail). If overboard, reduce to a mid-point, and keep rechecking/adjusting.
Break up the solid paint colors. You know about "cloud layers" but consider other things like light gradients (i.e. on the new c205 wings I did you can see this) and highlights on certain parts of the paint (on my p47s you can see this). Break the color up, be it with light, dark, gradiations between the two, whatever. Solid paint color looks like MS Paint.
Greebo's got a good tutorial there. If it's the one I think it is, then I've tried it also. I use a variation of the same idea, but more free-hand. I use it for wing scratches by the wing roots and areas that get scuffed up a lot. He uses them EVERYwhere (which is probably the better route to go!). I always have problems deciding on blending options for these layers, so I generally blend them over other layers to represent fading paint.