I've done 4-5 rear glass installs and agree with you, more difficult than the front. As mentioned by Patcon, hatch needs to be mounted on the car, install the rubber gasket on to the glass, install the SS trim into the rubber gasket. Lose the rope and get some string trimmer/ weed wacker line, install the trimmer line in the pocket that will go over the pinch weld, lube every thing up, I just use a squirt bottle with water with a small squirt of dish soap.
You really need a second pair of hands, close the hatch, mount the glass on the hatch, snug the glass down on the bottom of the hatch, that the will be the edge that gets installed over the pinch weld first. The last section of the rubber to be installed will be up near the roof.
One guy is inside the car laying on his back, the other outside. Start pulling the line over the pinch weld, once you have it over the entire bottom lip the guy outside needs to pull the glass down to ensure full contact. It is crucial that this step is done now, once the sides are done there will be too much fiction to adjust the glass.
Once the bottom is properly seated work the bottom corners one at a time, proceed up the sides equally, then the top corners, then the top horizontal section.
On the corners it is helpful to rotate the line in a counter clockwise circle to help the the rubber over the lip without tearing, also, once the rubber lip is over the pinch weld you will want to push/pull the lip down from inside with your fingers so it is fully seated.