alrite buildign a rodent rack and got the stuff for the auto-water system, i got 3/16 tubing just teeing off to each cage and a vari-flo valve

2 questions, how do you set how much flow you want, i mean i know you just twist em, but what am i looking for eigher rats and mice?

and also am i going to have to bleed the system cuz it seems like when i open the shut off valve for the first time, ill need to bleed the air out, whats the best way to do this?