It is easier to winterize by draining water systems than it is to fill them with antifreeze.
After winterizing the Lucky Devil (hull 109) for the first time, I found and read an article in TECHTIPS than detailed winterizing a 320. I'll admit I swallowed hard as I read all about flooding everything with antifreeze knowing that I did not use any. Come spring, the truth was made known. There were NO PROBLEMS. No need to flush the green stuff from everything and then find a responsible way to dispose of it. Interested? Here's how.
Starting with the boat on the stands in the yard, I first ensure all thru hulls are open. I remove the sea water strainer, drain it and clean it and reinstall it. I remove the hose from the discharge side of the raw water pump and blow thru it until the heat exchanger is clear. I also remove the raw water pump cover and impellor but that is more for the impellor than for freeze protection. That just leaves the aqua-lift muffler. After opening the drain valve and allowing it to fully drain, I loosen all the hose clamps and get enough rotation to get the remaining water out of the 'box'. It's a good idea to 'walk' the water out of the hoses during these steps by lifting up the low points but a little water left in a rubber hose is not a problem. Moving on to the fresh water system, I remove the cabinet in front of the sink. (after pumping down both tanks that is) I remove the hot water tank drain plug and manually open the relief valve. I disconnect the hot and cold water supply hoses at the TEEs and the open all of the faucets. I blow out the remaining water in each hose by blowing into the faucets with one open valve at a time. Leave all faucets open. Don't forget the aft station. Go ahead and run the pump for a few seconds too. Open the hand holes in the water tanks and wipe up any remaining water there as well. If you have a filter as I do, don't forget to drain it as well. It's the same game for the shower drain system and head. Open the system and drain out the water. It's not rocket science. It doesn't cost anything. It doesn't make a bunch of work flushing things out in the spring. It gives you a heightened knowledge of your systems which will pay you back time and time again. If your hoses are cracked or the clamps are frozen, you will notice and repair them before they make for a bad day on the water.