The way that I de-winterize is to hook up to city water at the house and flush all the lines, including dumping the low-point drains. I also fill the hot water tank from my city water connection, rather than let the water-pump work overtime. It also gets the air out of the lines. Then I fill and drain the fresh water tank, adding bleach to sanitize it from sitting for a couple of months. I then disconnect the city water and run the pump to get sanitized water through the lines, and the H2O heater. I let it sit for at least 24 hours and then dump everything. Then I refill the fresh water tank to half full (just my way of traveling) and refill along with the H2O heater. Then I am ready to go.
I have the ability to dump my holding tanks at home, but if I didn't, my first stop is at the local RV dump and I get rid of all the water that I ran through my system. I then charge my holding tanks with a couple of gallons of water, some holding tank treatment and liquid Calgon (just to keep the tanks clean).
I HTH