Easiest way to get started is to use compressed air to blow out the lines. Use an adapter to connect your compressor to the street water connection. Just be sure to turn your compressor down to 40 psi or so.
The mani bloc is not an issue as itís mainly a method to isolate a line if you have a leak. Sounds like youíve looked at your water pump and confirmed that you donít have a line to draw antifreeze. Donít think I do either. You could install one if you want. A trip to a camper supply to buy the valve and 3 feet or so of line. Obviously goes in the line somewhere between the tank and the pump.
Do you have bypass lines on your water heater? If not, thatís an issue also.
Bottom line, Iíve found the best way to winterize is to head south about Oct 1st.
2006 Gulf Stream Friendship G7
350 Cat, Crusier Lift w/ Honda VTX
Blue Ox and 2019 Chevy Blazer RS AWD V6