BradC,
I came across
this document regarding the use of refrigerant line dryers, from a Scandinavian site (I can't even tell what country).
Anyway, it is about using line dryers and most interestingly for you, quantifying the required dryer's capacity for removing a known (or estimated) quantity of water.
Though it might be useful in your quest for dry BBQ gas.
-AC_Hacker