Planning on trying saltwater etching for the engraving between lugs. There's a thread somewhere with some very encouraging results. Also have my eye on a laser engraver attachment for a 3D printer...less than $100, and if it can't do the metal, it could at least laser cut the stickers for the saltwater method.
As far as airbrushing for patina...has anyone tried dry brushing? In my youth, we used to dry brush models and figurines to give them an aged and dirty look, I think it would work the same on a watch dial.