[mike16]

for smaller parts I have used some of the electrolisis and chemical concoction you see alot of on u tube. its the set up that kinda works like a battery with a battery charger. Its worked pretty good at removing ruts but i dont know about bondo but it did NOT remove RTV/gasket material.

and yes there is a lot of junk in the bottom of the tank. I let the water evaporate and what is left over is disposed of with the local city recycling .

as for future rust prevention as soon as the part is removed from the talk it is sprayed with a high pressure washer that heats the steam to 300 degree's. until the part is very hot, hot enough for the water to evaporate off almost instantly, then spray it with WD40
It can sit for a while and only needs a good wipe down and prep to be ready for paint.

I have done alot of engine part and no sheet metal but the theory is the same, you just have to get clever with the tank design and electrode positioning. I saw somebody submerge an entire and complete exhuaste system for a 63 tempest and do that. the set up was actualy easy. but the electrode location had to be changed to do the entire system. cant be much more complicated than a door.