Adding weathered effect to hi-res skins

[FooFighters]

Hi there captains :arrgh!:

Does somebody know a good modding tutorial for adding weathering to skins.
I have both Jasc paint shop pro 7 and corel PSP 10.
I am working on a hi-res 2048 skin for the subs and want to release clean and weathered versions.

Thanks in advance

Foo..

[letterboy1]

Some mods take the weathering away, then others add it again. :D