There are kits that help deal with winterizing the water system. I've installed two of them. One sets up a bypass on the water heater. This re-routes the water so it never goes into the hot water heater. You then only have to drain the hot water heater. This instead of pumping 10 gallons of pink antifreeze into it.
This kit uses only one Tee. Some kits use two tees. On the 348 with inboards the water heater isn't easy to access. Using just one tee makes it less hassle. You just turn that one tee and now no water gets pumped into the heater. You then open the drain valve (likewise tough to reach with inboards) and pop the pressure relief valve to drain the existing water from the tank. Otherwise you'd have to pump antifreeze back into it and at $2-$3/gallon that's just a waste of money.
The other is a tee that allows using your fresh water pump to pull water from antifreeze jugs and pump it throughout the system.
Then you can use a blow-out plug fitting for compressed air to push any existing water out of the system:
Once you've got all the water out you can then pump the pink antifreeze into the system. You'd just open each tap and wait for pink to run out of it.
I also picked up a Camco hand pump. This will, supposedly, let me pump anti-freeze into other fittings. I'm guessing it'll be useful for pumping the pink stuff into the through-hulls for the AC and stuff. But I'm open to suggestions on how to deal with them.
I don't know the "right" way to deal with the ice maker (yet). It feeds off the cold water line to the cockpit sink. That tap has a shut-off valve to it. I'll have to ask U-Line about how to properly winterize it.