The De-winterizing suggestions above I won't address.
I will suggest a different "Anti-Freeze" however.. AIR. now it is indeed possible for Air to freeze (you don't want to know the freezing point) but if it ever does you won't be worried about your RV.
I like to open all valves including low points and blow gabriel blow.. I use a six gallon compressor with a pressure regulator set to 50-55 PSI, blow till the thing drops off then let the compressor recharge, like 5-10 times till I stop getting water or hearing sputter.. No problems doing it that way
Had a problem the one year I used pink stuff.