For winter months I always recommend that my clients just get a clay bar and a good winter wax. My focus for the winter is protection of the paint. I don't think it is worth it to take the time to polish vigorously to remove swirls at this time of year. This is because salt and junk on the roads will naturally create swirls that would have to be repaired in the spring either way, so, instead of polishing twice, just polish in the spring. For winter a nice glaze should suffice to hide swirls, improve gloss, and not sacrifice the clearcoat. My recommended pre-winter prep would be clay bar, glaze, and winter wax.