Why do they do this?
It's one of the easiest ways to dry off feathers. Their skin is oily anyway and if mixed with animal gut juices, it can become a very dangerous mixture of liquid with too much bacteria.
So in short, vultures dry off their feathers in this way to ward off bacteria and disease. They can also do this to regulate their body heat.
All this camera really got was this one turkey vulture and a solo raccoon.