I winterize with about 4 gallon jugs of antifreeze total. Drain the entire system including the water heater. Bypass the water heater. Put 2 gallons in the fresh tank. Run the pump and faucets until antifreeze shows up. Use the other jugs for all of the drains and holding tanks.
In the Spring, I use a pump and plastic hose to clear out the fresh tank, fill with fresh water and flush the lines. Drain the tanks again. Fill with water and sanitizer tab. Let stand for the presecribed time. Drain again. Fill and flush with fresh water two more times. Drain and fill. Open water heater. Run hot lines. Top off fresh tank and ready to go.