To flush I usually just shut off power and open the drain valve. The incoming water pressure helps force sediment from the tank.
To drain I shut off power, shut off water feed, open the drain valve and then manually open the pressure/temp release valve to allow air into the tank to displace the drained water.
To drain I shut off power, shut off water feed, open the drain valve and then manually open the pressure/temp release valve to allow air into the tank to displace the drained water.