Brent,
I've carried several deer out of rough mountains, but the way y our buddy does it would scare me a bit. The animal appears in too much of a "live" position.
I skin out the lower front legs to the knees, and leave the dew claws attached (break/cut the lower leg bone off, but leave the skin attached to the leg). Then I tie each front leg to the "gambrel" on the opposite back leg using the skin that's still attached to the front leg. The dew claws will keep the knott from slipping loose.
Then lay the animial on it's back, and put one arm between the back legs, the other arm between the front legs, and let the "criss-cross" go behind your head/neck.
Then stand up, and the deer hangs upside-down behind your lower back. You can grab the head/antlers of a deer to keep them from swinging, and hang your rifle from the back legs (which are sticking more or less straight up) using a sling or rope.
You can always hang an orange vest or other visible cloth from the animal if you feel it's needed, but the animal won't be in a position to look like it's alive.
I've never dragged an animal out of the woods, mountains, or desert.
Daryl