Ball pumping help!

I know I need a better 'jar' vs the 'tube' I have for ball pumping. My question is 'what pressure do you guys do when full package pumping in a jar? I'm trying to avoid the hard skin part at the tube bottom. A jar should help with that but I prefer not to donut up my dick. Love big balls but not a puffy dick. What pressure would be best? Any tips on working just the balls in a jar greatly appreciated. My ultimate goal is big balls with a low hang not a grapefruit with a stick! Thanks for help!