Couple things to add from when we had a "W":
I blew out the water system with a air compressor, 30 PSI, and then used two gallons of anti-freeze.
Water Filter tips: Blowing out the system first will get enough water out of the filter case it won't be as messy. If you want to save a little anti-freeze put an empty water bottle in the water filter holder after removing the filter. Just be sure to remove the paper off the bottle or it will turn to gunk in the bottom of the case...
Our low point drains were on flexible hoses, I had to fish around for them thru that access hatch. The low point drains had "caps" that only needed a twist to drain you didn't need to remove them.
Remove the drain plug on your water heater and let it drain. Release the pressure valve on the tank first
or expect a serious blast of water! You may want to replace the nylon drain plug with a brass kit with a petcock. That will make it easier next time as our was a total PITA to access.
It was about a 30 minute job the first time I winterized. Now that I know where everything is it would have been faster...except I get to figure out the GTS this year...