I have the propane style tank used for sand blasting and have spent many hours trying to get consistent results without success. I have installed a vertical pipe cross drilled to slow the feed rate of the sand in addition to the ball valve and it still gets plugged and stops the sand. One solution I have read about is to use a very good American made air drier on the incoming air to eliminate any moisture to allow the sand to clump and clog the output, the other solution is to add a mixing valve to the bottom of the tank and these are used in all professional sand blasters. But they are very expensive starting at $200 and jump to $400 and on up. I have given up but hope you have better luck. I believe a pressure washer with a siphon feed is the most economical and safer for your lungs. Good luck and invent a solution.