Can body filler get wet/dirty and still be OK?
 

Long story short, me and some buddies are going on a trail ride in our 4x4's. I had to weld up a couple patches where the previous own had a CB antenna. I need to skim coat the patch with some U-Pol Dolphin Filler (not glaze). So can I apply the filler, let it cure, and then be ok if it gets wet and so forth? Or is it gonna take in water and get ruined?

Bondo type filler absorbs water. Marglass, Bondoglass does not.