front-door weather stripping on a 1976 300D

I recently replaced the weather stripping around the front doors of my '76 300D. That seemed easy enough - at first.

However, I cannot get the plastic grommets reattached with the metal retaining strip that holds the weather stripping along the front of the door in place.

Does MB use an air gun or are MBZ mechanics endowed with superior strength?

No matter how hard I push I cannot gets the grommets reattached with the metal retaining stip in place. The best I've been able to do is to reattach the weather stripping without the metal strip in place.

How do I do this properly (with the metal strip in place)?

Robert