Not to say this is the " correct " way . But to clarify ;
I used Nylog Blue on the mating surface of the " stationary " brass fitting , inside and " back side " of the copper flare and inside of the flare nit . Also inside threads of the flare nut and outside threads of the " stationary " brass fitting .
I tightened it down , loosened it off and tightened it down . More than once .
I had obsessed about 45 degree or 37 degree flare . Pretty sure my old Craftsman flare tool was 45 degree .
To me , it appeared , the lubricated surface of both sides of the flare , would form fit to the brass ( the copper being softer ) .
So , to me , it seamed 45 degree or 37 degree would work it self out on its own . Either that , or I had lucked out & the correct flare tool , in the first place .
I started out with 50' rolls of copper , so I had plenty to cut off a piece of both small and large lines , to practice making flares .
Best of luck , my friend .
God bless
Wyr