Winterizing

This is my first year winterizing my R Pod. My next door neighbor told me the easy way he winterizes his RV. He uses a small portable sump pump in a 5 gallon bucket. Connects a short hose to the city hook up. Fills the bucket with RV Antifreeze (2 Gal) then turns on the pump. Opens each faucet, toilet, shower, outside shower ect one at a time cold and hot until pint antifreeze flows. Afterwards he adds the remaining antifreeze to the tub drain and the Black tank thru the toilet. Plus he drains his fresh water and of course he already drained Gray and Black. Ok so I did the same thing. My question is: What do I need to do to protect the 12 volt DC water pump. No Antifreeze is pumped thru the DC pump from the city connection. Do I just open the two low point drains on the bottom of the trailer? Will that be enough to protect the DC pump and plumbing. Should I open all faucets now that power is disconnected to allow for expansion?