In the same boat
Like the OP, I used EX-turn. The left master cylinder leaks at the fitting. I have not installed the forward baggage floor and have great access, and I can see the fluid coming out around the fitting, so I know this is where it is coming from. I drained the brakes and tried permatex with the same problem. After doing a few searches here, it seems Loctite 567 or Bakerseal are the preferred sealants, but it also seems that several folks have had success with EZ-Turn. I'm going to give it one more shot and it if it isn't working then, I'm going to swap the MC out and see if that does it.
By the way, I went ahead and swapped sealant on all NPT fitting on the MC. This is still the only one leaking.
Also like you, I have also gotten quite good at filling the brake lines.....