The general progression of evil goes something like swelling --> reduced blood flow --> increased friction in your tendons --> increased swelling. Ice or contrast baths are fantastic at reducing swelling, but you have to take care to let yourself warm back up before using your hands again. Trying to get work out of cold hands/wrists is a recipe for more of the aforementioned cycle of doom.

Wrist rests/wrist guards have dubious benefits. The do encourage proper posture, but you really don't want any pressure on your palms or wrists, since that gets back to the cycle of evil again. With even a cheap keyboard tray (I have a cheapo plastic Kensington drawer model that I screwed into the bottom of my desk), a better keyboard like the Kinesis, and so forth, you end up with your elbows hanging straight below your shoulders, so there's less weight that you would otherwise need to support on a wrist rest.