I found this while looking for something else.
“BERU glow plug assembly grease (GFK 01) helps against stucked glow plugs. Simply grease the thread and the shaft of the plugs with it. In addition, it prevents corrosion of the glow plug body and the penetration of moisture.”
A quote from: http://www.beru.com/english/aktuelles/presse/20040824-PI175.php

I believe Never-Seeze type compounds work fine on Glow Plugs but some people may think otherwise.

BERU pdf with Glow Plug cross reference and other information:
http://www.adpdistributors.com/beru_glowplugs_application_na2004.pdf

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84 300D, 82 Volvo 244Gl Diesel