Since the waste valves and pipes are the soft underbelly in freezing temps, I have a gravity-fed funnel-thing that I hook to my valve to backfeed the pink stuff. It can be as simple as one of those caps that has a garden hose fitting where you force it in through a short hose held above the pipe.
After every dump I replenish the pink, and as Gary says, the more pink in the pipes the better.
RE/Trailer chains, every state's laws are different. OR/WA/CA seem similar: Trailer drag chains required for travel in snow zones Nov-April, snow or not. On dual axles, rearmost only.