I have been using a TIP sandblaster for years and have had no problems. It is a pressure feed unit that holds 100 lbs. of sand. You can find them advertised in Hemmings. We run the air thru a refridgerated drier before use to eliminate clogging. When you blast, move the nozzle quickly and never hold it in one location for long periods of time. We use the above method and have never warped a panel yet. We usually use a 01 size blasting sand and blast out in the yard behind the shop. Good luck.