Interesting thread. I'm painting a pickup bed trailer, and just bought some herculiner for the bed yesterday. It was on sale for 69.99 at Checker (after rebate). Unfortunately, they told me one gallon would be enough. Guess I'd better go back and get more.
I've epoxy primed mine, and was just going to scuff it with a Scotchbrite, but I'll pay attention here for a while. Haven't got the shiny paint on yet, anyway.