You guys sure do things the hard way...why don't you consider covering the aircraft, if it' a representation of an aluminum skinned airplane, with "aluminum" in the proper panel shapes, to begin with. Then all one would need to add is the rivets, screws, access panels, etc.

I wrote an article for MAN on this very subject last year...if you can't find it, I'll email you a copy.

i.e. the cowling and strut fairings are of aluminum