Here's a suggestion for the guys who want a flat finish. A guy on another forum who does a lot of "rat rod" work (and is very knowlegeable)uses John Deere Blitz Black tractor paint and swears by it. Goes on looking like black primer, but won't weather and fade the way primer will. Very durable and inexpensive. Not sure how it responds to rolling, but it seems like it's in the same arena as the others. Worth a try!
Just my FWIW.
LanceB