Winterization is not one procedure. Plumbing layout, water heater type, icemaker, washer, and exterior shower all change what needs protection, so the plan follows the RV and its installed components.
Manufacturer instructions for those components set the sequence. That is why a written scope names the systems covered instead of describing a single drain-down that fits every coach.
Ask whether spring return-to-service is included. Dewinterizing is separate work and should be planned and quoted rather than assumed.

