Slufoot is right, the best breech plug lube is anti-seize for the majority of the breech plugs out there. I prefer Oatey's pink PTFE Tape because it works well, and is less messy.
However, bigblock455 is correct in this case, the new CVA breech plugs do not need any lube at all. These breech plugs seal so well, that NO blowback gets into the threads. I now use a light coat of quality gun oil on the threads when protecting the rest of the rifle/pistol.
Here is my Optima Pistol Blackhorn 209 breech plug after 3 primers and 21 shots at the first range session. I wish all breech plugs sealed like this. I no longer need the tape, as you can see.