If you using the old rubber you need an old priest and a young priest. New soft rubber it was easier to do the rope trick like for a windshield. Kinda hard to explain but put a small/soft/strong cord/rope in the rubber channel, get one lip in and while a friend holds up the glass you pull the rope from the inside pulling the rubber through. If that makes sense. There are probably other ways to do it but it works. The softer and more flexable you can make the rubber the better.