I want to build my own pressure pot sand blaster but I'm not sure whats needed. I have a 25 gallon tankon wheels that stands uprite with a 2" threaded steel cap w/oring seal. I know I will have to drill a hole in the bottom and weld a bung there, the top already has a fitting for an air line to be connected. do I need a special gun or will a regular gravity feed gun work? How much pressure should be in the tank? will I need to run 2 air lines one to the tank and one to the gun? Anyone build there own? comments and suggestions needed!