I have a HUGE warning about running the hot water tap to make sure there is water in the tank. If the BYPASS valve is still in winterize position (OPEN) and the in and out valves are closed, the water fill flow out of the hot water tap and the tank WILL BE EMPTY.
This is a horrible way to check for water in the hot water tank, IMO.
Use the pressure relief valve until water comes out before you turn on ANY power to the hot water heater.
With no water in the tank, using the VAC switch (outside in some water heaters) will destroy the element quickly. Using the DC/Propane system with no water in the tank may damage the high limit thermostat.
As to moving the switch from outside to inside; you really don't "move" it. It just stays "ON" and the outlet the water heater plugs into is changed to a switched outlet.