I bought used FF and I learned:
Take razor knife and gently cut off anything extending from threads where it was molded together and along the top of each piece where they meet f screwed together.
Screw and unscrew each connector 15x tp groove threads together.
go buy the blue plumbers tape(not the cheap white stuff),
Buy food grade waterproof lube, like keg lube from LHBS.
Wrap blue tape 2x around threads, in the correct direction.
Smear a reasonable amount of lube over heads and squeeze so tape conforms to threads.
Done correctly, I’ve ad no leaks in 3 batches. Keith