I just drew up my own plans from units I had seen for sale on net. Run it off my 16cfm compressor (12cfm free air) perfectly fine. Just have one of those guns with a suction hose on the bottom. The inside its angled down to keep the grit flowing through the gun and I have an extractor fan (bathroom unit with lights etc) to blow out some of the dust.
Rubber gloves are hose clamped to the enclosure and I have a rubber seal around the lid/glass window so its as sealed as possible. I wear a respirator while doing it to, to be double sure I don't breathe any of it in. Its VERY bad for your health. I use proper blasting grit, not sand or glass.
Any questions fire away. I don't have the plans anymore, easy enough to draw a rough plan and change it to suit as you go.
i use all 3 depending on the aplication sometimes i use presure pot with sand only on ally casings that are coated .or il use suction gun with sand or beads to finish off there is no health risk as the extraction fan can pull more air out of cabinet than the comp can pump in causing a vaccum .and if blasting outside just use the proper airfed blast helmet