Polypropylene long johns, which aren't visible under my normal CAS outfits, and wool socks. If really cold, I also wear a long wool Swiss Army overcoat (gray) that used to be avialable from Sportsman's Guide (for under $20 as I recall - may still be available, but not sure). I removed the epaulets, and replaced the buttons with some that were more period correct appearing. Only problem remaining is my hands - don't like to shoot with golves on.