When you have ALL the quests done, level 190, be equipted with Canopus hat,suit, and boots, Black Skull Duke gloves, and Dragon Saint gun.
have these skills in your hot keys:
Battleship
Battleship Cannon
Octopus
Support Octopus
Gravoita
Gun Booster
and Maple Warrior
Have these items for thier Attack bonus proterties:
Diet Coke
Halloween Candy
Steroids
Ale
Coke
Coke of Awesome
This is my setup:

Now youse Cookies and Cream Ice Cream for when its futile, cuz it fully heals Hp and MP and gives +100 attack for 30 sec.
Use Cheese and Hippies Water for your basic HP and MP repenilishing.
When you get the quest Talk to Whinry again, click yes. Now DONT move , if u get close it will wake up.
Use all buffs but Battleship because you cant use Gun Booster while in Battleship. Then use All items but Cookies and Cream, that is for dire situations.
Go into Battleship and attack with the Battleship Cannon, why? Triple attack and rapid shot do bout 7-10k if you have max Dex and with ALL items. Battleship Cannon does over 20k, and is rapid fire.
When your all buffed with items and skills, in Battleship, wake him up, and constantly use Cannon. use your Cheese and Hippies Water when you need to.
if you do this, you will kill him pretty quickly, Octopus and Gravoita hit more then 10-20k dmg.