THE BEST, and EASIEST product I have ever used on the aluminum door trims has been the Aluminum version on the rust (corrosion) removal product Naval Jelly.
The aluminum version was a pink gell that you simply brushed on, then rinsed off with water. This will leave the panels bright-white, completely free of contaminants. It's not a "polished" look, but far more natural, like brand-new aluminum. I'd think this would be especially more correct on a concours oriented car.
The problem with (products like) Billet, is than when you "polish" aluminum, you always get a (BLACK) residue and you'll leave it within the surface reliefs (texture) of anything but smooth aluminum.
I'll admit that I haven't seen the product on the shelves like I used to, but I haven't been looking for it either. Look for (the original) Naval Jelly, and if you can find that, the aluminum version should be right next to it.
Yep, still around:
https://www.acehardware.com/product/index.jsp?productId=1418919