First, get rid of the rust with vinegar or oxalic acid and/or aluminum fol rub-down. Then, remove the oxidized outer layer of paint with rubbing compound. Be careful around the decals if you want to preserve them, and don't get so carried away that you wear entirely through the paint. You just want to remove the dull, oxidized stuff. Finally, a coat of automotive wax and some elbow grease to bring up to a nice shine.