We live on the Lake Michigan shoreline in West Michigan approx. the same latitude as Grand Rapids and we almost never winterize until the Thanksgiving weekend or later and have never had any freezing of waterlines or filled items in any of our RV's over the last 52 years of our RV'ing.
very wide, deep, and long Lake Michigan takes most of the summer to heat up to the mid 70's+ and then takes most of the winter to cool down to the upper 30's. The lake never freezes solid but rather just gets a thin layer of ice near the shoreline. Heated rises from the summer warmed water naturally and that warm heated air blows right over us as our prevailing winds come from the westerly direction. Thus, much warmer near the lake in late fall and winter than inland 25+ miles or on the Wisconsin/Minnesota side of the lake as they get bitterly cold over there. Almost never have any surface ice on the river or Lake Michigan even near the shore until in January. Per the TV weather reports and trivia yearly around the holidays, 68 out of the last 100 years we have had a green Christmas as in no snow being on the ground here.
Heck, the shipping season for cargo ships don't stop coming and going here or on the great lakes until about the end of January and restart approx mid April. Lots of CG's and several State Park CG's are open all winter in Michigan and we used our RV's all winter long for snowmobiling up in the Upper Peninsula. Even Tahquamenon Falls State Park CG in the U.P. just a little ways from Lake Superior is open all winter and we have stayed there several times.
Therefore, living here, our answer is that we only gravity drain the water out of our RV's after Thanksgiving Day and seldom blow out the lines and have never put pink antifreeze in any of our many RV's. Besides, that's what water in 2 gallon or jenny jugs is about and using of a porti potti that you can dump in any toilet or pit toilet are for, so winter camping which has no "closed for the season"! Using windshield washer fluid which is good for -20 to -30 F in your porti potti flush tank and it never freezes nor does the stuff in the bottom tank as that's where it goes when you flush. Who'd a thunk it?