RE: Anyone used Harbor Freights 20lb pressurized sandblaster
ditto to what Jason said. I have a similar model and they are very picky about dry air, dry media and the size of the media. Mine will not really run on the avg. "play sand" that a lot of folks run through the cheap siphon feed units. I eventually starting using professional media in mine and blasting on top of a giant piece of plastic. Then I recovered, filtered and sifted the media and re-used it.
When it works, it works a HECK of a lot better than a siphon unit.
Also, good hood is mandatory. Media gets places where you don't want it.
Also, most any sand blaster or media blasting cabinet requires a large volume of air. Pressure is easy to get, volume requires a big (2 stage or better) pump.
I have an Ingersoll Rand 6.5 hp, 60 gallon single stage compressor for now, when I get my shop built, I am going to replace it with an IR T-30, 7.5 hp, 2 stage, 80 gallon unit.