I have used the ketchup and salt trick a few times on my Prometheus Lights (DarkSucks) Beta-QR copper, and while it did clean up fairly well, it only lasted a day or two and seemed to tarnish much faster. Most of the time I let it stay tarnished for a cool look and also when it's tarnished I don't mind using and abusing it. Yesterday I went out and bought a tin of Nevr Dull at my local auto parts store, and WOW.
Edit: After 2 days it is starting to patina again, so the Nevr-Dull didn't last much longer. However when I did the ketchup trick, the patina was more yellow in color, rather unappealing. This time it looks darker like regular tarnish, much better.
After 4 days: