paint touch up

The previous owner of my bike dropped it and dented the side of the gas tank, which in turn scraped off some of the paint. Now some of the "spots" where the paint came off (not really scratches) are starting to oxidize and rust ever so slightly. Is there anything I should put on this before applying touch up paint?

I'd rather not get a new tank, repaint the entire tank, etc. (i.e., do it the "right" way). For me, it's not worth the time, expense, effort, etc. I just want to stop the rust from spreading and cover up the defect somewhat, or is the "right" way the only way to stop the rust?

Keith