I use 40 psi and 20' of 3/16ths. Dedicate a keg to soda to save on o-ring replacement.
If you want to do a fast force, put 4-7 lbs of ice in the keg, then add the makings and top off, leaving 3-4 inches of head space. Seal, pressurize and shake. If your back can't handle it (like mine), lay a a couple 2x4s on the floor and rock the keg. AKA the kids helping option.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk