I have just finished painting and weathering my 'psberetta' gauntlet missile. The quality of his work is outstanding and his communcation is excellent, if you have the chance grab one of these.
HERE'S WHAT I DID:
Firstly, I didn't use special paints or primer (specially made for aluminium) because I wanted to be able to peel off the paint to get the correct effect.
I started by airbrushing the bronze coloured item (and part of the neck) a little darker using a metallic tamiya Brown. I then masked off all none black areas and airbrushed a Tamiya black acrylic. That's all the painting done.
Now the weathering. Before the black paint is fully dried I pressed masking tape onto the surface and randomly removed portions of black, this worked very well. Then I airbrushed a mist of black over the front of the bronze coloured piece. When dry, I dabbed on a mid grey over the black using a sponge (just on the bronze piece). When dry, I lighlty rubbed this piece with a mild scouring pad to bring out a few little hilights, be carefull not to remove the bronze coloured paint that was originally applied.
Next I needed to dull down the whole thing and give it a dusty effect. I did this by airbrushing a mist of mid grey, this toned down the black and dulled the aluminium nicely. Then, using a scouring pad I gently rubbed the aluminium areas to remove some of this grey paint, this makes the aluminium look tarnished and dusty.
I haven't sealed the missile as mine will be displayed on my mannequin and shouldn't get knocked around. The paint has keyed very well to the missile, but If you will be trooping in yours then you should really use an aluminium primer on all the painted areas.
I hope this makes sense.