WW -
You could, but probably a bad idea. First, the metal in the diecast car isn't the same as the fender / body walls of the real McCoy, so the "defects" wouldn't be the same. Second, there are fairly common places were Mopars (and most cars) tend to start rusting, and usually predicted patterns of rust progression. Since you're an armor builder, use the same skills. Get pictures of a similar car that has the rust pattern your trying to emulate. Make the "holes" with a Dremel or similar tool, and then paint accordingly. There are a few posts around about making "rust" by oxidizing steel wool, etc. First thing is to know exactly what you want it to look like, and second, make it happen. There was a picture if an old green Superbrid in FSM or SA, that had been laying around for a while in a back yard, that one was scarry, the car and the diarama looked too real. Also, take a look at www.junkyardjewels.com, and to answer the first question you'll have when you get there, YES, they're models!!! There are a few guys on the web that do this kind of stuff, but these are the best I've seen.
Archer out.