I use this:
Aquatank IIand the on-board water pump to transfer water from the bladder into the freshwater tank via the city fill port.
To accomplish this, I hook up the bladder to the winterizing port, move the lever to "Winterize", and then hook up the fresh water hose to the outside shower by unscrewing the shower head and using one of
these adapters.
After running the fresh water hose from the outside shower to the city water fill inlet, I open the cold water valve on the outside shower and turn on the water pump.