I use one to pressurize my wax injector. I’ve got it on a foot-
activated switch, so it only comes on when I stomp on it. I’ve got a
very small hole in the airline, so it bleeds down to nothing in about
30 seconds. In use, I can vary the pressure on the injector for each
mold, without having to use my hands. I just stomp on the switch,
pump it up to whatever pressure I need, and shoot the mold. By the
time I’ve got the next one ready, it’s dropped below where I need it,
so I just pump it up to wherever, and go again. Very handy.