Mr. Tmater is right. I once wrapped a sock around a spindle to paint the body of it and forgot to remove the sock. When I did the spindle was completely rusted and destroyed. All due to the sock collecting moisture from the air.
When I get a new panel I spray it with epoxy (assuming you do have a compressor) and that holds up to the weather for a long time and you can sand it a bit to add any filler you may need. Even if there is some dolly and hammer work, I would do the same thing and just sand down where the hammer strikes were made and spray again.
