I did it exactly how the dude in the video did it. And that's use Overdrives when you are about to be swarmed with a large number of enemies at once.. and to kill the final boss as quickly as possible. Not even letting her unleash the horde of rockets.
It worked for me easily.
Beware of he who took them, he goes by many names. The Bogeyman, the Shadowed One, but all are he the same. Remember to always behave, for sins he wont abide. He wields a rusty, jagged blade to cut out your insides. The bullies and their spiteful wrath will find torment as well. Soon he will strike them where they stand and drag them into hell. So do not cry aloud at night, stay hidden in your bed. Or the Bogeyman from Silent Hill will come chop off your head.