Instructions
Choose the command "Mist" and select "Quickening" for one of your characters during a battle. This character will perform the maneuver and the screen will pause for your next move. A timer will begin depleting.
Start another "Quickening" with a second character or press the "R2" button and wait a few moments for the "Mist Charge" command to appear. Perform these actions before the timer counts down to keep the chain going.
Press the corresponding button for the Mist Charge (depending on the character this could be "Circle," "Triangle" or "X") to give the character performing the initial Quickening one more level of Mist Charge. This will let him perform another Quickening in a matter of moments. When the command appears press "R2" to perform the Quickening.
Press another button ("Circle," "Triangle" or "X," depending on the character) to make another member of your party perform a Quickening. Keep this chain going until you run out of Mist Charge for each character.