Well thanks for the help guys. I do appreciate it. The valve/hoses arrangement on this thing are all clustered together and I simply missed the hose under the valves that returns to the tank.
Obviously the "mixing" question is no longer an issue. I can just add the stuff and turn the pump on, flip the bypass valve and let it go to town mixing itself.
I really appreciate the food coloring suggestion. Easy indicator of proper mixing.
My old sprayer was only 30 gals and I could shake it around enough to insure everything was mixed. This thing weighs over 1,200lbs when full so shaking it was out of the question. Guess I could have run it down some railroad tracks...LOL
Actually a half a mile of rail bed is one of the things it's going to be used for. Our rail spur gets overgrown with weeds/grass about twice a year. Weeds grow vigorously all year long down here... once the summer weeds die in winter the winter weeds just take their place.... of course winter down here is lows in the 40s most of the time with a very rare freeze
...Which is one reason why we are all here. 
