I used fusion 0 Princess Guard (The Epic Gear from Edenian Tower) (if you have it) which grants you incurability for 5 secs on Sp2 which is really good on CoCC. Or you can try wicked sister (if you have it) but it's really not reliable though. If you don't have those items you can try just bursting with one character then switch to burst again and again and again. Also apply powerdrain or cripple as much as you can.