I don't officially winterize our PC but I do drain all water from all fresh water systems. I am impressed that 99.99% of the water comes out via gravity alone from all the pipes. I open the hot and cold drain valves (to the street) located in the outdoor storage compartment, open the kitchen & bathroom faucet, shower & outside shower, and HWH, and it all drains out. I know this because when I use compressed air to eject the last of it, just a few drops of water comes out. It appears that I only have to winterize the traps. It would be nice if there was a means to blast the water out the traps, then drain the tanks and forget the pink all together.
I am sure each PC model has it's own characteristics, but our 2007 2350 self-evacuates exceptionally well.