What is the best way to clean a tuba mouthpiece to make it shiny again?

Answer 1

use some anti-tarnish solution (you can probably get this at your local instrument shop or hardware store) and scrub it with a non-abrasive cloth/sponge. The rinse it out (so you don't get the solution in your mouth).

Answer 2

coke. it sounds weird, but it contains acids that will eat through a nail and get rust off your bummer, I swear it will work!!