So, if you read the article on the "New Quests Added" the guy in the barbossa suit was holding the cutlass in his hand like holding a staff while charging.
Well, I found out how to do that
How to do it:
First of all you need a staff. Go to flaming skull (I think that works the best). Charge, and when it gets to about the second 1/2 notch, push esc (do not stop charging though!) then quickly change to a different weapon (besides grenades, grenades dont work xD)
It might not work the first time (cuz u probably did it too early or too late) so just keep trying.