If this were your brand new, ride-it-all-the-time, sexy custom steel beauty with a candy apple Joe Bell paintjob I might offer some different advice, but for something you admit you haven't used in a while, my first thought is "Do nothing."

Besides, rust on the outside of a steel bike frame is ostensibly protecting the steel. It's not a virus! Unless you leave you bike outside exposed to the elements 365 days/year, I'll bet you could let those rusty paint chips fester and multiply forever and the frame would still outlast you.