After perusing the web for all the different ways of getting rust off of drum parts, I decided to try "evapo-rust". Wow, this stuff is great! Worked much better than any of the other methods I've tried, and is very gentle on the metal. Can be used multiple times before it stops working. And it's non-toxic, can be disposed down the drain or dumped on the lawn. And pretty much odorless.
It was not easy to find. Neither Ace, HomeDepot, Lowe's, or AutoZone had it. I was about to order it, when I stumbled on it at O'Reilly's.
Anyone else try evapo-rust?