Anti-Seize & Lubicating Compound
Slowhand get a can of antiseize compound at the hardware store I like the 'silver' kind that has nickle flakes in it. A 4 oz can should last decades. Put just a dab in the nipple threads, and you'll never break a nipple wrench, or strip the threads on a breach or cylinder. My can came with a brush in the cap but I use a safety pin to apply this to the threads, just a tiny bit goes a long way.