What I've found that makes an excellent metal finish is Testors Metalizer polished with Scotchbrite. Discovered this by accident when trying to remove Metalizer from some parts.
I use Metalizer in rattle cans for convenience. The trick is that you have to spray it onto bare plastic - NO primer coat. The lacquer will bite the surface of the plastic and that is the key to getting a good result, IMO.
What I do is to assemble the part/model and dress all the seams. Then I spray on the Metalizer - onto the bare plastic. Light coat at first; you don't want the lacquer crazing the plastic. Then polish that out with Scotchbrite. What you end up with is a finish that looks like the back of a polished teaspoon, depending on what shade you use. Very convincing.
You get two other results with this method as well - 1) the Scotchbrite also removes any Metalizer residue that may rub off during handling; and
2) the finish will naturally "age" or tarnish over time if left unsealed...which also looks pretty realistic.
At present I've only used this technique on small to medium sized detail parts, but I have a Trumpeter Bear J that I'm planning on doing this as the overall finish, using several shades of Metalizer. I'll post pics on ABMS once it's in paint-up.