Mine are just starting to go. I was hoping someone made rust repair patch panels like the ones available for American trucks. Those are nice, you cut out the rusty section, use patch panel adhesive to put the patch panel in, fill, prime, and paint.
Unless it's rusted through, you could always go the cheap/easy route and sand it, and then apply some Rustoleum Rust Restorer. You knock off any loose rust and spray over the remaining rust and it converts it to a flat black paintable surface. There are other professional rust converters out there as well, but probbaly cost more than 6 bucks a can like the rustoleum stuff. I used it on the bed of my truck here (http://www.toyotanation.com/forum/showthread.php?t=354145&highlight=rust+treatment). I havent had the bedliner back out to see how well the Rustoleum stiff is holding up, but maybe it's a start.
Also, I believe Chip n Oreo has been doing some bodywork. He may have a few good solutions for you. Good luck! :thumbsup: