73 Duster - how to removal rear windshield = want to reuse gasket and glass

I've done it a few times. Once went to a parts yard to collect reveal moldings and gaskets from a 69 Notch back. Yard owner said, " Break that rear glass and you bought it. Additional 40 bucks." It wasn't easy.
The guys in the clean up shop had a 5 gallon bucket of silicone/armoral like stuff that they used on tires, interior, etc... so I had a about a quart of that for soften and lubricate in a pump spray bottle, and a helper. By the time the glass was out our brown cloth gloves were soaked. Cleaning a used gasket for reinstall is a chore too. Bottom line,
Big mess to clean off the car and clean that used gasket versus buy a new gasket.