I think a buffer would be a bad idea. I'd look at how your storing them if something is going on with them. Last time I looked at mine they still look brand new.
You can get silver polishing cloths. My gf gave me one, yet to try it. You can clean with chemicals which I have found very successful and easy/quick, but if you're holding something rare then chemicals might not be a great idea.
http://forums.silverstackers.com/topic-2194-wrapping-silver.html http://forums.silverstackers.com/topic-2280-coin-cleaning.html http://forums.silverstackers.com/topic-7426-maintenance-of-silver-coins-bars.html