Well, if the path is a deep rut and the snow is hard and crusty you're probably SOL. But otherwise, you can brake using only the tail of the board. You basically turn very slightly towards one side then throw the tail against the side of the rut. It's enough to slow you down. To stop you'll basically have to do this more aggressively and climb the side and stop.
I'm sorry. Was I talking while you were interrupting?