I'll be interested to see what others say here. I have a possibly brass, possibly copper shell that I purchased as NOS from eBay. I used a lemon on mine (actually three now that I think of it) and it cleaned up pretty nicely. Elbow grease really had little effect. I just needed to get the lemon juice on the shell. I spent maybe 30 minutes on it. I have a thread about it but searching from my iPhone seems to be a bit odd. The thread is "putting snare beds in a brass shell" if you want to see the progress. Again, I put very little effort into it. I could clean it up better with a little more time and couple of additional lemons. It will need polishing after. Also, the drum smells really nice now.