How about waxing it with carnuba wax? I was told to use it by a person who was in the business of buying old featherweight machine and selling them. Her machines all look brand new when she sold them, even though they had flaws and some were really old.
I would highly agree with not using any kind of cleaning product that is stronger than water. And by all means, don't let it dry on its own, whatever you wash down, wipe dry immediately.