[dsraven]

I always wait the required time after the first epoxy application because, firstly, I apply a good thick coat of epoxy and if there were rust pits those sections are for sure heavily coated. I try not to use a panel with rust pits that bad but if i do they get heavily coated. anyway, my point is, the epoxy needs to gas out on t's own thoroughly so I give it that time to fully cure before i sand on it. too early and it comes off the metal as you sand because it's soft. with a thick coat of epoxy it takes some time to gas off so applying another product on top means you may get a great mechanical bond but it doesn't matter because the gas from the previous coats is gonna come through and either make bubbles on the next coat of otherwise affect it. i have had the bubbles happen to me once. it took a long time to sand that all off and start over. not gonna do that again. maybe a body shop that works with new straight panels could pull it off with the chemical bonding theory but I will stay with my tried and true method.