'0000' gauge wire wool works well with polished parts. Too fine to scratch but still strong enough to clean up the metal when used with a decent metal polish.
The wire wool also gets rid of water marks on glass windows too.
I find Meguiars metal polish better than autosol, also brings up the exhaust quite well, just keep rubbing it in until the cloth turns black, lot of people don't work it enough before removal/buffing off.
If it's just from a drip, and more of a residue rather than a stain, I've found that vinegar works well. Just don't rub too hard to start with otherwise it can scratch. Works well on external paintwork too - especially from a leaking garage roof!!