I'm getting started even earlier this year on my "Christmas" layout. The example I'm starting with uses cotton batting for the "snow" but pretty much rebuilds the entire layout from the base up every year. I'm having enough trouble getting it built the first time and want to minimize having to replace a ton of material each year. I'm even considering something that I can run year round.
What are the techniques you use for winter layouts? Do you use cotton batting? Do you sift "snow" over everything? Do you add "sparkle"? What do you do to make it look like a winter day?