You can use any umbrella to protect against the roar, even the basic one. While he's roaring I usually sneak around to his back with the umbrella up, then whirlwind slash him as he comes out of it. When there isn't the second ape around anyway.Took down Snake Eyes #2 last night on first try as well, felt pretty good, then I pushed my luck with Headless Ape and he took me down on the first two tries. I could have sworn you could use Finger Whistle on him and have the two fight each other, but apparently not? Seems dumb considering animals/beasts are listed in the description. So I was using fire crackers on Brown Ape, and hitting Headless with the Spear for additional posture damage, but still got caught by the terror roar and said oh well.