3M 08509 (Auto Bedding and Glazing Compound) is what I used and is really good on the outside of the weatherstrip. Mask the body with good quality masking tape carefully around the edge of the windshield gasket (right up to it), use a very good caulk gun and when you're finished wipe with naphtha or mineral spirits on a cloth...not soaking wet, just moist. If you also mask the outer edge of the gasket you probably won't need to clean up much. I know some folks use the urethane stuff, but this 08509 never really dries. It stays tacky (according to 3M) about a day past always. On the inner part (where the gasket meets the windshield), you can use 3M 08693 (Auto Glass Urethane Windshield Adhesive). That will bond the rubber to the glass nicely. Same sort of clean when using this and you can mask around the perimeter (on the glass) if you want to make clean up easier.
