Better than a wet rag
I learned the wet rag between the chimney and the cap on my BGE here, but I
don't remember who to credit it to, and couldn't find it in the archives.
On my last gasket replacement, I had just enough left over to gasket the top
inside rim of the damper cap, works like a charm, even better than a rag,
and 'cause I never remember to soak a rag first.