My brother used to install 200 per day on the assembly line. They used to pre head the rubber before installing it to the glass, On cool Northern Calif days the rack of ready to install glass had a bank of heatlamps. Most guys used soap but he could install them faster using kerosene but it leaves a smell for a while. He overlapped the installation "rope' on the bottom so it was doubled, I still have the rubber hook tool. A 1/4 inch shank screwdriver was chucked in a lathe , A ball was formed on the end then a long taper back, the shaft them polished. The end was heated and bent to an L with a 1 in long elbow. when the rubber does not pull in easily you could "help " it with the tool and not tear the rubber lip. They used to use a rubber hammer to "help seat the glass. but with out a lot of experience knowing how hard to hit , they can break. I also have the rope tool, a screwdriver with an oval ring on the end shaped and a slight fold to install the rope to the rubber in about 10 seconds.
be sure you check the windshield flange for ripples , sharp spot weld flash, etc , I always use a hammer and dolly to work the flange as smooth as possible