I use this product called Bluemagic Polish Cream, i bought it at Target( I think) but you'll find it at any Car Shop.
Remove the keys from the bass and unscrew all the components.
This product is blue, apply a little bit on a paper towel( you can use a rug but I think you'll have to throw it away) and scrub it on the part.
You'll see that it turns black, and the part will be really shiny.
I'll attach some picture to show you the results.
The only problem I'm encountering (on another bass) is that I still see a film on the chrome that is not coming off, if you guys have any suggestions...
