cleaning the pins of NOS tubes...bad idea?

If you are not absolutely sure that your contact enhancer will not rub off and bake into and onto your tube socket, then don't use it. Instead, as suggested, do a very light sanding or buffing of the oxidation.

Pencil eraser and alcohol wipes. Safe, effective, cheap, tried and true.

The **most** I ever use is a simple contact cleaner like you get at Radio Shack. After cleaning the tube pins, I wipe them down to remove all excess.

The reason I am careful about this is it is very easy to contaminate the base of the tube and/or the socket itself. Some contact enhancers are conductive or have capacitive effect, or break down in the presence of high voltage. Some 'enhancers' and creep from contact to contact, causing reduced performance!

You can RUIN your equipment if any such materials get into your sockets- I've seen it happen. That is why I am very careful about this. Some sockets have really high voltages across them at turn on and certain materials can contribute to arcing. That can damage the socket, possibly an output transformer or power supply part... its not worth it,

Im always careful when handling tubes, as they dont tolerate any kind of oils, like the ones we have on our hands. I generally use contact cleaners.