What I Would Do In Your Case
There are two keys I use to gett the bike's rubber back down. First is to make sure any pulling force I execute goes through the center of my body/ back and through my feet as much as possible. It is o.k. to reach "over" a down bike as long as I am pulling horizontal "through" my back instead of an offset lift that will stress my back. (Say like pulling on the handle bars down hill). The second key is to get good traction. Combining both key items as a last resort would be to lay down on the ground (or against a tree) and push the bike, tires, handle or whatever with my arms or legs. There is a reason one can bench PRESS more than they can lift.
Looking at your bike and assuming I could not move it the way I was lifting I would look to change my approach. Is this on a switch back so I could go down the hill to solid surface? Either way since I would want a running motor to help me get the bike up the slope so I would get the front and rear wheels even on the slope. First I would try tugging the front wheel up hill, rotating the bike on the foot peg. By pulling from the front of the bike tire I can get some leverage to make it rotate around the foot peg area. Key here is to get traction (feet) as far as possible from the bike foot pegs so can use leverage. If pulling on the front tire UP did not work I would try pulling the back tire DOWN the hill just a bit till bike was parallel to slope. Either way once parallel to the slope, it should be easier to get vertical as it is already part way there (I would then lift from the "high" side"), pushing down against the tire contact patch that hopefully has traction now that they are parallel to slope. Perhaps the back lift on you tube would work then but it does not seem to help me. Better to get "under" the uphill handle bar and just lift strait up (again being sure lift force goes straight down through my body, not offset to my feet). Once the bike is vertical I would start it and use the motor to help me walk it up the hill. I might be walking just barely vertical to the slope but as long as I am making progress to the road I keep going.
I think I would would definitely carry some kind of 30 ft (or more) 2" (or wider) tow strip / seat belt webbing in case the above approach did not work. Then I would loop the strap around the forward portion of the front wheel and around my waist then get up on the road (where the footing is good) and then walk / tug the front wheel up hill. If still could not get bike vertical then switch loop back to back wheel, go back up to the road and drag the back up a bit. Then repeat on the front wheel then back wheel crab walking up the hill till up. I have done this without a strap and it still works but much harder. If there is a thick tree up the hill to loop around then I might try using it as a pull so I am pulling down the hill to get the bike up. Or use the technique just to pull the back tire down the hill and then it vertical, start the motor and power up the hill as mentioned above.
If I did a lot of "lone" riding, I would consider some kind of solidly mounted back luggage rack. My stock KLR rack has slots that serve as an excellent "hand hold" for getting the rear vertical. Similarly, the front engine drop guards make it much easier to lift the front. Which end I lift depend on where I can get could traction. Our WR just does not seem to have anything to grab hold of in the back.
Better than all the above is of course to either ride with other riders (or where there are hillbillies) and/or to be more careful when alone. A guy in Houston got his leg severely burned by a heavy bike that he could not get out from under fast enough. To mitigate this risk, I always wear full gear including gloves, full face helmet, knee pads, kevlar lined riding jeans, and tall motocross boots when off road alone.