I only open my low point drains, along with all my faucets and shower, and let them drain.... especially if while driving the last several miles before storing it. I also do the same for the water heater plug.
I don't use the pink stuff or air. If the water is out, there's nothing to freeze... though I'm sure that many will argue that you can have water trapped in various places like p-traps, ice maker, etc.
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