I use a compressor and regulator for the water system. Once the water starts spitting and water heater is dry, remove line coming from the water tank and connect air line, set pressure to 30 psi. Open up valves and let the water start coming out, don't forget the head. While doing that I'm changing oil and other things.
You should have closed system and assuming no sea strainers except for Gen and A/C.
The hose from the drive will need to be removed from the pump. The hose will need to be lifted up and tied off up high long side the motor. Some will use a short piece of PVC to stick inside intake hose.
Get a deicer/bubbler to place under the hull.
Blow air out thru the sea strainers, then use a shop vac to suck out excess water left behind