The oldtimers' trick was to use brake fluid on the rubber gasket, and about a 1/4" diameter nylon rope to wrap around the pinch weld groove in the gasket. Use a piece of masking tape about every 6" around the outside edge to hold the rope in place. The tape tears away as you pull the rope, and you can remove the pieces as you clean up after the job. Rubbing alcohol or Windex will remove any brake fluid residue. I guess silicone spray would work, but we didn't have that stuff 40 years ago when I started installing windshields.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!