A buffing wheel was the way I used to buff all metal... Remove a bunch of parts and go into the garage with compound(s) in hand and work the cloth wheel.
Since then I found that for regraining ball guides, ball troughs, metal ramps... even touching up wire gates that have lost their lustre, or controlled gates with rusty flaps the sanding pads are awesome. I still use the cloth wheel, but not all the time.
http://www.canadiantire.ca/en/pdp/glit-sanding-pads-3-pk-0542186p.html#.UyUB0T9dUn8
Pads are just that much quicker, and often you don't even have to remove the parts. I've carefully done ball guides and metal ramps in game after taking some time to protect the PF. It really depends on whether you are stripping the PF in the first place, or doing some touch ups. Of course it's always best to remove the part from the game and work it on the bench. The sponge pads work great on curved parts, fold nicely into places like ball troughs, and they seem to last a long time. Price is right too.