I just saw a thing on TV where they used cornmeal in a sand blaster to remove paint, varnish, etc. from wood. No damage to the wood, no health risks, and cleaned it quite well. When they were done, they just swept it all outside and let the birds take care of the cleanup.
It looked like they were using 50 lb bags like is used for cattle feed.
Maybe you could use it in a cheap airbrush type gun.
I don't know about plastic, though. Probably depends on the kind of paint used.