Like mentioned I usually just drag them guts in back to the truck or near camp this keeps them clean. With deer their antkler tied to the rack aren't an issue but with moose or elk I pull from the hitch or ball off of the animals neck then just secure the antlers to the rack to ensure smooth dragging. This way I don't pop my front tires off the ground or worse flip over when going up inclines.
I load deer solo by using what is like a ladder. Basically 2 - 2x4's with 1x2's rungs screwed on every foot or so. Roll the deer onto it, then rope or strap the deer to the rung side of the ladder, so the bottom remains flat or smooth. Pick up the one end set it on tailgate, trailer, etc and pick up the other end just slide the ladder onto or into whatever. Depending on your rack system you may need to modify it by u bolting on a piece or plywood or something to create a solid surface in which to slide the ladder.
The other way is winch/hoist tie off, move under and release. Just be careful loading it on a truck with the extra weight if placed on the back rack.
FYI for anybody who it may appeal too. If you have a trailer and truck an easy way to load animals is by driving the atv on the truck backwards, securing it to the truck with tie downs then hook up your trailer, using the winch and ramps winch the animal on the to trailer and gone. Works great for elk and moose, really almost seems too easy.
Good luck