Matthyj, thanks for that reply, and talc is what I was trying to come up with when I said "chalk". I'm going to have to go back to town and talk to my paint guy again. It's always a learning experience for me, and I often amuse him by trying to take copious notes, and then reviewing them with him I'm thinking that the key is that some people tend to see the hi-build as their "primer" and just shoot their finish over it once they think they're done.
You mention shooting epoxy over the finished high build, but then you say that after blocking there's a "sealer" coat. What are you using for the sealer?