I also get better results with the two man method. The pressure/vacuum/check valve devices do work enough to get the brakes into serviceable condition but I am not happy until the job is finished with the traditional method, you can feel it in the pedal.

There is a little baffle in the brake fluid tank that separates the front and rear systems. If you go to flush, open a front and rear brake and pump until the fluid is below the baffle. Then carefully pump fluid through the rear brake only until that side is clean. Now you can clean out the front by adding fluid to the rear side until it spills over the baffle, but keep the level of the dirty side below the baffle or the dirty fluid will mix again.