I have had great success shooting vinyl (bumper/flexible) paint. It's a nasty substance tho, so buy the $50 gun and throw it away afterwards.

Dial in at 45psi and like 30% paint to air ratio, then 3 to 4 coats. Experiment on something else (dog dish). Prep, prep, prep... tri-sodium-phosphate (tsp) is an excellent cleaner, take your time and shoot everything at once.

VALSPAR REFINISH

PRIMER: PR3 FLEXIBLE 2K POLYURETHANE
ACTIVATOR: HPC000 URETHANE

FINISH COAT: 345 VINYL TRIM
SAME ACTIVATOR

and yes, keep your butt off them for 30 days if possible.

Johnny Mac

PS. I forgot, I bought two guns and pitched them afterwards (1-primer, 1-finish)