When I was a lad we used to mix vinegar with borax to clean copper and also good for cleaning lime-scale from taps. Just spread it on, lave overnight and rinse next morning. Borax and honey also cleans a furry tongue.
Whitening toothpaste works wonders. Not as abrasive as metal cleaner but still enough to remove marks and blemishes from the metal. And brings up an awesome shine
My copper 4nine got car polish and car wax over a week ago, it seems to be lasting nicely. Nothing too aggressive like t-cut, just some of meguiars two step system