Rear glass installation 1938 Pick up

[ms fowler]

Is there a trick or secret? I am helping a friend and we tried to put the rear glass in yesterday. New rubber gasket, dish soap and water as a lubricant and it still did not want to go.
Also, the screws for the interior trim are a problem. the screw holes in the back of the cab are perfectly horizontal, but the screws in the trim look to be at a 45 degree angle.