Gaff in the head, get control of the bill and lift over the side. Yeah, sword's in the boat! Now kill it quickly (billy club or hammer, I prefer a claw hammer (the claw particularly) right into the skull between the eyes) so it cannot dance around and bruise meat and make a bigger mess. Gut it and pack it well in lots of ice. Back at the dock, make sure you have large area to work in, lots of bags for steaks (vacuum sealers are great), and a good sharp knife. Fillet as per usual. Cut the huge slab of delicious meat into appropriately thick steaks and trim off the skin and bloodline. Bag and enjoy. Not hard, just a lot of work with a big fish.
And whatever you do, try not to drag your steaks around in the blood, intestinal juices, and slime. And no fresh water on fish. And COLD meat cuts a lot easier.