Last week I actually used a spray wax and coated the underside of my G37. We'll see if that helps this winter. I also waxed all the door jams, sunroof rails, under the hood and under the trunk. Plus the entire car has been waxed three times in three weeks. So other than snow tires, I think I'm ready to do battle with winter.
I've actually been using paint sealants instead of wax this year. They go on and off just like wax, but they come off easier and with less dust. And they last longer. They can be more expensive than your off the self waxes, but I think they are worth it. This is what I used on my G37 the last couple of weeks:
http://www.autogeek.net/wg5500.html
later,
Curt