Depending on the aircraft full power is not needed on the good engine. I had not seen the technique of reducing both to idle and then pushing one up.
With a Seneca II (turbo), a technique is to block the rudder pedal so full rudder is not available. Limit the power to a low cruise setting, simulate power loss on one engine, try to maintain altitude as speed decays to demonstrate the effects of Vmc loss of control and proper recovery. It will happen at a higher airspeed because of the limited rudder available and the effects of less than full power.
I'll agree that with a lighter Twin Trainer (Seminole, BE95), a full power technique can be used, but many will limit the use of full rudder to demonstrate loss of control but make it available for recovery.