I know I'm a bit late on this subject - but here's a long standing solution that I have used. It's called "Rector Seal" (no nasty comments please!). I first saw this stuff nearly 40 years ago as an aircraft mechanic working on C-141 for Uncle Sam. It's a thick paste and has been a standard for high pressure gas (liquid and solid) as well as hydraulics and fuel (JP-4/5). I have used it in all types of threaded lines and never had a leak. Just brush it on and tighten - wipe off the excess and viola.

It's available at Home Depot, Lowes or any plumbing store. Has an indefinite shelf life (I been using the same can for twenty years!)

Regards All,
Glenn