This can be done without any pushing.

Use momentum and gravity - hold it so that gravity pulls the insides down and then use your hands to "hit" - in turns - left and right side in the "up" direction (momentum keeps the insides in place while the "hit" causes the shell to move up).

Do it as in the video, use fingers, don't use too much force, and add some wiggling to the sides and it will come up easily.

BIG THANKS!

I’ve just fixed my old Nexus 7 2012 thanks to cheap new screen from China :D