If you just have too. LOL the best for no damage and a good PIN cleaning lowrider57 hit the nail on the head.
If you want to clean but not remove material and POLISH pins. Get a small handful of cotton balls and put, Deoxit, Rislone, or gun oil, on the cotton. DON'T get crazy, just a bit, and plunge the pins several time into the cotton. They will polish right up. Wipe off the excess. I leave a thin film on the pins..
Some of the old valves have a powder type ID. BE CAREFUL it will rub off, no oil or alcohol on the writing, ok..
Regards