I picked up a used industrial cabinet with a dust collector and filtration system. The gun that was in cabinet wasnt great, i picked up one with assorted orfices and nozzles.
And glass bead works about the best. I run around 70 psi.
I used crushed glass for an old pickup cab and did not have any distortion. Very economical. For really crusty stuff black beauty works pretty good...not sure what it is to be honest.