Close the valves on both the hot and cold lines attached to the heater tank. Open the valve between the hot and cold lines.
Flip the valve next to the water pump to allow the anti-freeze to be sucked in via the port on the side of the camper.
Submerge a hose in a gallon of pink stuff, attach it to the port.
Turn on water pump.
Open all faucets, hot and cold, including outdoor and indoor showers, keep open until pink stuff fully flows. Fill and flush toilet several times, letting pink stuff run free.
Make sure you do not run out of pink stuff while doing this.
With another gallon of pink pour it down the drains to ensure no water left in P-traps.
Drain fresh water tank. Seems fresh water still remains in tank even after a full drain, so you may want to pour a couple gallons of pink in there, too, just be aware that it will take a lot of flushing in the spring.