What's the best way to clean vacuum tube pins?

Instead of steel wool use scotch-brite.

Dweeler, I bought something from Audio Advisor called socket savers. 2 cool little nylon brushes that work perfectly for cleaning 6922 tube sockets and larger things like xlr sockets and power tubes....I've used them for several years now...

Well, after all of the cleaning, what kind of sonic differences did you notice?

dip them in cleaning acid. You can get it at hardware store. Be careful of course.... Dip pin only in a small glass container / small glass bowl or pyrex (only about 1/8 to 1/4 depth of acid) for about 30 seconds and then neutralize in baking soda solution (water and baking soda in another glass bowl for minute or so. Wash tube with joy and water if possible. Will remove any chemicals bonded when tube was made. no need to sand and works better. Acid is cheap, couple bucks for small amount. obviously only small pin tubes - works great on NOS nine pinners.

I use a tool called Fyberglas Rush eraser. Its bristles extend and retract with the twist of the cap, almost like a tube of Chap Stick.

The fine fiberglass bristles are self replenishing in that they wear away as they clean. Polishing tube pins with this tool works as well as the Dremel and avoids the steel wool and corrosive acid problem, requires no electricity or special skill and is inexpensive.

http://www.eraser.com/browsecat.cgi?mode=open&id=113

I told Michael Percy about this 10 years ago. I think he sells them now If you don't want to deal with The Eraser Company.