Meyer,
That is correct, only on the molding posts to seal the moldings at the top roof line and on the side/corner trim pieces (front and rear). There is another 3M product that can be used in the windshield/back glass seals. It's called Bedding and Glazing Compound #08509. This product should be put into both the front and rear seal grooves prior to installing the seal onto the windshield/back glass pieces. It doesn't get hard and shrink up which helps to keep water out between the seal and the glass units after installing them into the car.