You have to hold the dead man valve and it is always in the way to get inside of things. I use ball valves everywhere on the my pot blaster you can control pressure and sand flow. . You can prevent metal war-page when blasting sheet metal from the inside. low pressure and less sand when doing between the bracing on a hood or roof etc. If you use high pressure and high sand flow you will see the bracing on the outside of the hood / panel when finished. Seen it on my roof years back when I had a blast company doing my cars in the 80's.
