71C Drain Plug Leaking

My personal preferance is teflon tape, with the caveat of that you don't put it on the first couple threads. It's a bsp/npt fitting that seals by the metal threads basically gnashing together.
I get the 1/4in width mil-spec stuff i have at work, but you can easily use the home-depot stuff and trim it down with a razor. That way the tape is smaller than the fitting
and less likely to go over the first couple threads. You can fold it back while wrapping too, but it's quicker if you have narrow stuff to begin with.

The reason you don't want it on the first couple threads is because since that part is typically tapered, it doesn't act as a sealing area and the teflon
tape can unravel in that section and get into the process. A little can be really bad for microchanneled coolers like i plumb at work, but it's probably not desirable
for transmissions either. I've had bad luck with seized drain plugs which i guess also influences my use of teflon tape on them.

Loctite 565 is another option i use, but when you do a lot of fittings, it kinda gets messy. It goes on like toothpaste and cures in the threads, but can still be removed when necessary.

Paste is the way to go to take up some space in the threads. Compare the price on the Permatex thread sealant with teflon vs the loctite 565 to see if it's cheaper where ever you decide to buy.

https://www.youtube.com/watch?v=T94ZWgvHvns

Thanks guys I will get at it soon.

does it mate against a machined surface? If so, a copper washer might be a good solution.