don't pump, ABS systems do better dripping out which is why the Motive Products 0103 Power Bleeder works well.
It keeps the reservoir at a constant pressure and with enough brake fluid in the Motive, you don't run the chance of running the reservoir too low and introducing more air into the system, no need to have the second person pumping the brakes.
If anything, they can monitor the brake fluid in the Motive and also the pressure, which ... when you first hook it up, the instructions say to not fill it but pressurize and make sure there are no leaks in your braking system