About to rip my eyes out (Chapter 10 spoilers)

[Wolf Kanno]

Start the battle with SEN/SAB/SYN and simply buff/debuff what needs to be done. Then alternate between RAV/RAV/RAV, SEN/COM/RAV, and SEN/MED/COM when your sentinel starts taking too much damage or Cid's attacks start nailing other weaker characters.

Once you break the SOB switch to RAV/COM/COM and be sure to time your attacks so Cid is left in the air constantly and is taking constant damage. Its pretty easy to max his stagger gauge and basically murder the SOB, it just takes some time to get the rhythm of the earlier part of the fight and like BoB said it involves patience. You mostly need to just make proper use of Sentinel Class. It should be a constant use until you stagger him.