The only big difference in the winter for me is, I use hot water to mix my ONR.
Admittedly, when it gets well below freezing I slack way off. If it's been well below freezing for too long and the car's getting too nasty, I'll swing into a coin-op and hose the car down just to spray off the worst of the build-up. No garage here, so whatever I do is right out in the elements.