If it is a small bit, I've sometimes used wadded up aluminum foil, usually with a bit of lemon juice. While I get, conceptually, what the lemon juice does I'm not sure it really does anything here. It takes some elbow grease but it hasn't harmed the surrounding paint. If I have a lot of chips or what not, I'll still break out the Oxalic Acid bath...which is cheap and involves a lot less work. Then I'll clean thoroughly and usually touch-up with clear coat nail polish (sometimes a matching color)...sure, you still see the chip, but then I can also see if the rust comes back. I guess I figure that a metal colored chip looks better than a rust colored one.

When I do all this, though, it is never with the intent of restoring a bike or not seeing where the chip was, etc. If you go that route, I'm sure the prep and execution of the touch-up would be more involved.