I use the pink anti-freeze only, because it is so much easier to pump into the system (my air compressor is several hundred yards away from the camper, and an air tank takes several trips), gives reliable and positive confirmation that there will be no freezing, and only takes about 1 1/2 gallons and about 20 minutes, including external shower. In the spring, about one hour is sufficient to reverse the process. Just don't trust the air system, as air can blow over puddles of water, but anti-freeze gets it all. JMHO.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.