Bearing that in mind, I'd like to make the case for just doing more wax type product. Dismantle a bit if possible, then pressure wash, or ideally steam clean what you can. Remove anything loose and prep/treat/paint as you choose anything with surface rust and make sure it's not rusting through from the inside out. Then treat it all with a decent wax, dinitrol is pretty good but any are better than none. Won't be as tough or long lasting as a hard coating but with periodic investigation/reapplication is pretty good. Plus, adding another layer is way easier than going through the process of redoing a paint. Swings and roundabouts really, I guess it depends a lot on how long you want to extend its life and how big a job you reckon it's worth doing!