Here's the easy way to get maxed out hits (1000) without needing almost any timing skills. The "cheap" way if you will.
Target him, and just press B repeatedly but slowly enough so that you won't start doing that whirly twirly crap that'll let you get hit by him. Now whenever he tries to hit you just press R to raise your shield, it is the quickest and safest way to defend against him. You can tell he's gonna attack pretty easy... he'll raise his spear, you can hear your sword hit his spear (the sound), the rumble letting you know you could parry (don't parry), sword turning green, "A" button flash, sound Orca makes, etc. And try to keep him in the open so your sword doesn't smack a wall or an object messing you up, you're safest in the middle.
Eventually he says "enough" and tells you he lost count of how many times he got hit. He calls you his master and gives you a piece of heart.
One last thing is that you should use the Master Sword since that Hero Sword has shorter range I believe. So it is best to try this after Tower of Gods.