Best way to winterize yet still use unit in winter?

I agree with others. At the end of the camping trip, blowout the lines. The next time you will be ready to go.
You could add a little (1/2 gallon) of antifreeze but then you would have to get that out of the line the next time if you use the water lines.
We always carry 1 gallon water containers when we leave in the winter. Our water lines have the antifreeze in them until we get to OK or TX.