I think this has come up before. 2K is nasty stuff I wouldn't go spraying it in a shed. 2K products are definetly better than 1k though. My prefered way is to spot sandblast the areas. You can get sandblasters that have a rubber nozzle that you push onto the panel and the sand simply recirculates around. Note if not careful this can still raise the metal. Next step 1K etch prime nothing even comes close to Wattyl super etch for superior grip and corrosion properties except 2K. Note you can't do filling work over any 1K product. Ps the Wattyl super etch will handle 2K primers over it. What I generally do is strip the panel and etch prime if I am not going to do the repairs straight away, next step is the repairs, if I don't finish them in one go I re etch prime (I just leave it in the gun so it's always ready). I generally finish my repairs of in 120 grit dry, too smooth no adhesion too rough lots more chance for sink backs. When finished apply whatever Hi fill or spray putty you like. Hope this helps.

Cheers Dave