Well I have a much smaller TT (X19-H) without anything as fancy as the Nautilus. This works on smaller trailers, and might work on a big Northpoint.
I start by removing the external shower head from its hose, and putting the open hose end into the fresh water fill. With the pump off, turn the cold tap on for the outside shower. Inside the camper, stick the winterizing hose into a 5 gallon jug of fresh water, set your valves to winterize (close fresh tank, open winterize) and then switch on the pump. The pump sucks water from the jug into the system, and spits it back out the shower hose into the fresh tank. Switch off the pump while swapping out out 5 gallon jugs. It takes maybe 2-3 minutes to drain a 5 gallon jug this way for me. Helpful to have a spotter outside in case the shower hose pops out under pressure (or carpe ductum) Just remember to carefully undo all of the setup before switching the water back on again. Nothing more frustrating than forgetting to turn the shower valve off and having that nice fresh fill pumping back out onto the ground
Note, I used to just use a funnel and jug to try to fill through the gravity fill, but that always ended up with as much water on the ground as in the tank, and holding up those big jugs is heavy at the start!