Pour milk, cream, sugar and vanilla into small can. Cover the can and duct tape well. Shake the can to mix. Put a layer of ice and rock salt in large can. Insert small can and layer more ice and rock salt. Cover and duct tape well. Kick or roll the can for 10 to 15 minutes. Remove and open the small can and stir up the ice cream. Re-tape the can and put back in large can with more ice and rock salt (make sure there is always salt and ice in the can). Kick or roll for 5 to 10 more minutes. Open can, stir and enjoy with cake, cookies, fruit syrups, or just scooped into a dish.
Tip: The can will get cold, even frosty, on the outside, so kids may want to wear gloves to shake.