Main water line off, hot water still trickling out of basement shower

Close water to entire house. Go to the lowest plumbing fixture in the house (basement ?), open hot and cold water. Also, go upstairs and open h/c water valves in tub to allow air in. Go to the heater, close cold water and open open T&P valve, and turn gas down to "vacation". Otherwise, it will keep reheating water and hot water will be overflowing to the system and down to the lowest fixtures. Wait ten minutes for hot water to drip out of the system.