CO2 pressure is not too hard to control. When I used CO2 during my Sanyo #2 repair, I was able to dump the output end, into a little tub of water, so I could tweak the valve to get a slow stream of CO2 bubbles in the tub..
http://ecorenovator.org/forum/geothe...r-project.html
There's a picture on my set-up in Post #1. The CO2 tank is over by the floor jack..