I did it!!! (Almost), I actually overshot cutlass and mastered it seconds before the rest... oops!
Anyway, this is what I did.
I brought up all the weapons to about 6795/6800 on level 29, so each had about 5 reps or less before leveling up and mastering.
See that pic.
Like I said, I overshot the cutlass just seconds earlier, no biggie! The rest of the weapons were good to go!
Then I engaged a high level enemy using all the weapons, I specifically used Tim Dartan in padres' beach.
The result? MAJOR glowing!!! Leveled up everything and mastered all at once! How cool can that be!?
See the pix below!
I have always leveled weapons evenly and back to back, I posted something similar when I was mastering me previous pirate but I never leveled ALL of them at the very same time!
And BTW, that's also how I got the El Padron Lost Sword!!!