Here's how my friend did it:
On the branch, when it flies under and around Frosthold, he followed TLPD to a small cliff edge where there would be a lot of harpies. He was just out of melee range, so he fired off an Icy Touch and one-shot it. It landed on the cliff edge, and he couldn't loot it. No lootarang. Death Grip it to the tree on this cliff and spam Blood Boil to AoE kill it.
On the mountain top, facing the metal hole in the adjacent mountain, he was well in melee range for his first Vyragosa kill.
On the cliff overlooking Brunnhildar Village, his Icy Touch was in range to hit Vyragosa in his next two kills.