I don't know of any method Buick used to improve adhesion. All I've found is paint right on top of the chrome, not even any primer. These days, there are adhesion promoters avail to etch the chrome. For small items, it's probably not necessary.
For interiors, I use either spray can gloss black, but misted on to kill the shine a little, or a urethane mixed with a little flatting agent and applied with a small spray gun.
Isn't the grey actually silver?
For exterior chrome, I just did the grille and headlight doors on my 66 today. I polished the chrome with fine steel wool, masked the chrome off with masking tape, then sandblasted at a low pressure with aluminum oxide/glass bead mixture. That etched the surface nicely and cleaned out the minor pitting. Any pits were gone over with a small, fine stone on a dremel to smooth them out a bit more. Finished it off with a few coats of black urethane and some flatting agent. I'll get a better look at it tomorrow when I can put it on the car!
