Using plastic bags to create a Vapor Barrier Lining
When I know the ride is going to be very cold, I put a plastic produce bag over my foot, then a wool sock, then another plastic bag. The first one acts as a vapor barrier to keep your insulating layer/sock dry. Water in any form in an insulating layer draws heat away by conduction. The second layer over the sock, acts a an air barrier which allows the air trapped in the insulation to retain it's heat better. Used this trick in the military with good result.
You foot will sweat a little to start, until the moisture level reaches an equilibrium. After that it won't feel sweaty, clammy or cold until you stop for the day and remove the inner bag. When air reaches the skin at that time, it will feel damp and cold.