Depending on the coach, there may be a piece of tubing dangling on the suction side of the water pump. If so, just put the tubing in the jug of antifreeze, open the valve, shut the feed valve and run the pump until the water from all faucets run pink. Some hot water heater may have a bypass valve, if so drain the HW heater and open the bypass. If they have a aqauahot, that has it's own set of instruction as does the icemaker.
A lot depends on where they are located. Here it gets into the high teens, low 20's and I never winterize. Just leave the Hurricane set at 45 on days the forcast calls for a freeze.
Tough to think about winterizing when the temp is 106 outside.