Rather than using "heavy duty rubbing compound", the next time your at your local hardware store look for some "Dico CHROME, CR1" buffing compound.
This comes in a cardboard tube that is about 1 inch in diameter X 5" long.
It is a fairly hard, dark red wax like material that is made for polishing metal.
Although this particular compound is made for polishing steel I've found that it is excellent for polishing aluminum, brass and copper as well.
Normally, it is used on a cloth high speed polishing wheel but with a bit more effort it will work on a low speed buffer.