Since from your e.mail address you appear to be on a campus ---- Talk to
someone in the physical science or engineering labs, and try to scrounge a
tube of Dow Corning high vacuum grease.  This stuff is very inert, quite
harmless to paint....  I brush it around the opening before reinstalling
gasket+glass.  Makes reinstallation a comparative breeze.  In ~30 years
(good heavens!) of following this practice, I've never had any recurring
rust problems.

Glenn McComas, Queenstown, Maryland
87 Vanagon; 69 Baywindow; 87 v.d.p. XJ6; plus some cars that run.