Friend had has Pontoon trailer sandblasted what would be the best paint to use on it?

if Sherwon Williams still sells their industrial epoxy it was the best bang for the Buck

Ayuh,..... I find Rustoleum industrial enamel, with majic hardener to be inexpensive, 'n extremely durable,...

Imron direct to metal

PPG Delfleet Essential direct to metal . Don't expect the final look to be as smooth as if it was primed /sanded etc . That will apply to any paint on top of just blasted metal.

I am not a painter, but I just bought an equipment trailer and sanded it and painted it with Rustoleum Farm Implement paint from Tractor Supply. The stuff seems very durable and even for a novice like myself went on easy. Ithink you could roll it or spray - I sprayed and thinned as per the instructions…..

Came here to say this.

^^^^ If you roll it on, use a velvet roller. I find them at Lowes. They leave a very smooth finish.