When I got the blank I started out by throwing it around on a concrete slab (mainly to dent the emitter face, but also to create random bends and scratches) Then I deburred it in my case tumbler, which removed machine marks, dulled the surface and softened the edges. Afterwards I darkened the metal with a bath of diluted Easy Off and applying Aluminum Black with a rag (focusing on the booster area)
For weathering the paint job I started out by using Trooper_trent's stencils. Then I removed some (freshly sprayed) paint randomly from the edges with a Q-tip dipped in paint thinner. When the paint was cured, I applied a wash of diluted acrylic copper paint on the windvane, then I buffed the whole thing extensively to emulate years regular handling. That's pretty much it!
Here goes!
