In regards to weathering though, my thoughts are that the surface you are weathering would been dulled off over time, the only surfaces that would be still gloss would be in the case of a new vehicle that has got dirty, (mud, dust and the like). I havent progressed to using powders and the like, just using what is at hand basically to ry and re-create what I think things would like. At the moment I am trying to make a 1940 Ford pickup (hotrod version) look like an old farm work vehicle.