Meanwhile, soak the pork or sheep casings in warm water for 30 minutes. Drain the casings. Working over the sink, gently run warm water through each casing. Pinch both ends and lift up the water-filled casing. Look for any spots that leak and cut out those portions.
Place the sausage stuffer in the freezer for 15 minutes. Set up the sausage stuffer and slip all but 6 inches of a casing onto the tube, leaving the trailing end untied. Tightly pack the sausage mixture into the canister. Start cranking the sausage stuffer very slowly until the meat emerges from the tube. Now tie a knot at the trailing end of the casing. Slowly crank the sausage into the casing, using your free hand to regulate how tightly the sausage is packed; make sure not to overstuff the casing. When the casing is nearly stuffed, tie off the end.