To me the buckles in 1:48 are small enough that when I make masking tape belts and straps, I just cut the ends to the shape of the fastenings and draw a silver area on the end with a silver fine tip marker. That doesn't work for 1:32, but looks fine in 1:48 and 1:72 Aircraft buckles generally are not chrome, they are some duller coating, maybe zinc or something like that, so they don't need to be super shiny.