He wasn't new at this. He wasn't even wide-eyed and half-spastic the way Jo had been when she first started hunting.
You didn't get to Hell and back without knowing a thing or two.
Dean knew two things, alright. One was that the hair on the back of his neck was still, in fact, capable of standing upright, despite everything he'd been through. He attributed that to the sheer novelty of this. The movie Wolfman wasn't real. This was not a thing he'd ever hunt. But it's howl was fucking horrifying.
The second thing was that this kid was not human. Dean felt his guts kick at the observations he was making, the realizations that followed. He didn't think, though, because the kid had a point. He just fired, hitting the Wolfman in the calf. Hip would hurt more, but it'd also take longer to heal, and Dean didn't really want to hurt someone more than he had to.