Is he worried about a freeze off if the worst happens or simply wants to shut of the heat and power (which is not the same thing as shutting off utilities)? Asking because during storm Uri early this year, a lot of folks didn't winterize and normally wouldn't have needed to but when the power failed....it got truly colder for longer than pipes could handle.
Anyway, I winterize my cabin. For drain lines, shut off toilet supply and flush the toilet, pour RV antifreeze in toilet and sink traps. Do not forget "hidden traps" such as washing machine standpipes or AC condensate lines. Do not forget floor drains. For appliances like washing machines and dish washers, you will need to read the manual on how to winterize. For instance, with a washing machine you may need to start a cycle, and then close off the taps because otherwise the cycle won't start if the machine can't detect water pressure at the inlet. For supply lines, shut off the inlet of course. Empty the water heater, pressure tank if there is one, and drain all other lines by opening all faucets and other drain points and keep the taps open. Ball valves may have little drain caps on them, crack these and leave open. Don't forget outside hose bibs. Don't forget "hidden" supply lines like an ice maker or a whole house humidifier. Empty toilet tanks and remove the fill valves (i.e. ballcocks). On tub/shower combos, pull the tub spout valve to activate the shower so the slug of water in the shower head riser can drain out of the tub valve. On stand up showers, it may be worth pulling the shower valve if cold temps are expected soon so the riser to the shower head can drain if the supply lines enter the valve overhead. All of this is usually sufficient unless you either have long length sagging pipes with low points or expect temps to get really cold quickly. PEX is fairly cold tolerant so probably not worth the hassle of compressed air. CPVC and copper less so, but will not burst as long as freezing expanding water can make it's way out.
