I may do a little Overkill when winterizing, but I first blow the lines out with air (I've got a 60 gallon air compressor in my shop) and then I fill/flush the plumbing with RV AF.
I run enough through each faucet to replace the water in the drain trap with AF. Our camper takes about 2 1/2 gallons to get it done.
No freeze damage anywhere yet.
Don't forget the outdoor shower!!