Winterizing black water tank

[N1VWD]

Hello to all in the group.
I live in VT and I am in the process of winterizing my TT for the year. I have read that after draining the black water tank you should always add 3 to 5 gallons of water to the tank to keep any remaining solids from drying out and keep every thing in solution. Do you still do this at the end of the season? What about freezing, wont it damage the tank? If I drain the tank what about any residual nasties left behind wont they dry out.
All replies will be greatly appreciated.