I really like this product:
http://www.brownells.com/.aspx/pid=1...UST-PREVENTION
In my opinion, this is the best product you can use on guns that you just want to preserve and not shoot. I believe it's a mix of wax and some petroleum based solvent, so the bulk of it will evaporate and just leave a very thin wax film on the parts. It also has extremely low surface tension, so it tends to spread and creep like no other product I have seen. I dip or brush the parts, dab off the excess and let them dry overnight, this will displace water and leave a very thin waxy film which protects well. Granted, it's not as hard and dry as carnauba wax, but it's way easier to apply and not nearly as greasy as oil. You will also need to use a little lubrication on some moving parts if you intend to shoot the gun.
Edit: I might better add that I have heard about people using car wax. Some types of car wax also contain a fine polishing compound, and I wouldn't use anything like that on a gun. If I were to use wax, I would make sure that it's pure wax and nothing else.