The primer is for lack of a better term is soft and scratches easy. It also is starting to chalk up where the sun is on it all the time (I park under a carport). The neighbor across the street did an old pickup with a flat paint and he says his scratches easy too, but his is holding up to the sun. This may be why your painter advised you not to. I wanted to paint my top with a urethane and the jobber at the paint supply said you could not flatten it out enough because of the hardener, so I ended up using an acrylic enamel on the top. It was a little strange to paint with because it seemed like it did not have a lot of pigment and more of what he added to flatten it out.
I have seen some urethane flat black (rat rod black) but don't really know anything about it. There has to be something out there. it seems to be a popular color.
I am sorry that I missed your message somehow and just saw it. I would have replied sooner. Thanks so much for the kind words and hope you have as much fun as I did, it was great therapy. I really did get a kick out of your post on the black and the use of the word "murdered out". That is what a surfin buddy calls mine. That is actually epoxy primer that is on it now and everybody was telling me not to paint it because they loved it that way. I am going to eventually paint it probably the silver it was originally. If there is anything I can help you with, do not hesitate to ask. I am picking up another project Saturday (fingers crossed) that the wife had to have and should be posting that up soon under other builds.