I use a Camco hand pump and pump antifreeze through the black tank flush. I normally do this at the last campsite after dumping and flushing the tank. I winterize the plumbing first, then I leave the black tank valve open and pump antifreeze in until I see the pink antifreeze flow out through the transparent elbow. Then I close the valve and pour 1 gal of antifreeze into the black tank via the toilet, leaving a bit in the toilet to keep the flushing mechanism wet.
Enrico and Donna + 2 kids
RAM 2500 + Jayco Jay Flight 25BHS
Black tank Quick-e Flush, MaxxAir Vent cover, TV bracket and LCD TV, added Slideout awning, bunk ladder, added socket and reading light to top bunk, added bathroom fan switch near light switch, insulated all externally accessible storage, sealed pass through storage from interior of trailer, LED lights throughout, added LED lights to storage compartments