Here is what I do for seating stainless steel lines to the brass fittings.
Make sure that the brass fitting seats are clean.
Install the brake line into the brass fitting and tighten it snug without the wrench slipping of the nut from overdoing it.
Back off the nut slightly, then snug it back up again and pay attention to where the wrench ends up once it is snug.
Do not remove the wrench as you tighten and loosen the nut.
You will notice as you tighten and loosen the nut numerous times, the wrench will end up further clockwise each time.
Once the wrench no longer moves the wrench further clockwise as the time before. you have completed formfitting the stainless steel flare to the brass fitting and you should have no leaks nor boogered up flare nuts.
