I would like more explanation as well. There are six aux out pins. The linked mixing page does not show clearly how to access these pins. I'm using actuator_controls_2 and getting no output as I clearly haven't set up my mixer correctly.
I can get aux1/aux2 RC passthrough but I don't want that. I want to set a servo action waypoint and have the pwm on a given aux out port go to a set value to actuate a servo. This is all working except for actually getting the desired PWM on the given aux out port.