Use only the MB specfic sunroof grease. It doesn't harden, it's waterproof, and it doesn't attract as much contaminents as spray-n white (litheum grease).
Rather than purchase a giant tub, call Randy at EPS Parts (http://www.epsparts.com
) and he'll fill a 35mm film cannister with the grease for about $2.25.
1988 360TE AMG