ploly-fiber or Stewart system - roll on metal coat ok ???

[Geowitz]

As far as the Stewart System - You should be just fine especially if you're gonna have the top coat sprayed. All of their fillers and primers are sandable so even if you do get a few bumps or roller marks you can easily sand them out and reapply if you need the depth. Or you could just add an extra coat, sand smooth, and take it to the paint shop. Rolling it on shouldn't be any less rugged as long as you keep the coats light and apply with the same timing as if you sprayed.

I love the Stewart System. Lots of flexibility.

Edit: Sorry, I was just referring to the Stewart System. Can't speak for poly fiber.