Want to set up a new rig and need some help. I would like to know how to setup the mixing side of it. Do you guys use 3 tanks or 2? As in do you use an SH tank and water tank and have a way of mixing before it gets to the hose reel or do you have a mixing tank as well. How do you set the amount of chem that goes in? Do you have to watch it or have you some way to preset it?