Rubbing with any cloth will work for most clarinet players.
For reconditioning clarinets
I find these two products work well for all keys and other metal parts of clarinets:
I also use Miracle Polishing cloths:
I cut these into smaller sizes, and store the cloths in a sealed zip-lock bag. This keeps them from drying out, which makes them not work so well. I like to use these cloths for the posts, tenon rings, and other metal bits that are on the clarinet body.
New infor from Robert Bauder:
MAAS doesn't do nearly as well as Diamond Brite Truck Box Polish, using paper towels as the delivery method.
For chrome plated keys (and not so useful for nickel keys) this vibrating polisher works well. This has crushed walnut shells in it which bounce against the keys and clean them.