start of body work

One thing you can do, if you are worried about storage or being somewhat weatherproof, on a temporary scale, is to sand one panel to bare metal at a time and coat with epoxy primer.

Acid etch/ wash primers are only used in a dust coat. They go on very lightly and are not going to keep the area/ panel from rusting if exposed to water. Typically, I use Acid etch primer as an adhesion promoter and surface prepping agent for urethane primer, just before I use the urethane primer. You shouldn't need to sand acid etch. It's a chemical bond and should be followed by another primer, after it's flashed/ set up.