Please, I'm begging you, someone give me some help with the Nameless Puppet [endgame spoilers]

I'm on NG+ (I gave up after about 15 tries on NG and just gave up my heart. I'm trying to get the platinum and am trying to get revenge. Yes I do understand that it was stupid to give up my heart on my first playthrough).

I have died to this little shit at least fifty times over the last three days. I can't tell you how many times I've gotten him down to his second phase and about 25% health, but once he enters his berserker mode it's just impossible not to get stun locked by his damn waterfowl dance things.

My current strategy is to get him to phase two, without any consumables, then at the start of phase two use the perfection grindstone a few times to build up some stagger, then once I get to the halfway point I throw every consumable I can carry at him, especially shotputs (I can carry 6 at a time), I'm using electric blitz abrasives also.

What other things can I possibly do to make this work? Any amulets other than the Puppet Destroyer's Amulet that are especially worthwhile?