Teflon tape is NO GOOD. It's designed to LUBRICATE tapered pipe threads so that they can be screwed tightly to make a METAL TO METAL seal. It is NOT designed to act as a sealant or for anything else. The last thing you want to do there is to lubricate it.
(1): degrease the threads on the BBL and the threads in the can with a good degreaser, like carburator cleaner. You want a no-lube situation.
(2): Crank the thing down! Don't be afraid to tighten it like you mean it. The threads are FINE PITCH
(correction added, see post below) ones, it'll unscrew, no worries. Be manly!
Ought not be any need to use loctite, etc... just not needed if you do the two things above.