Depending on the size of the animal we use about one full can. As we spray them, we rub the disinfectant into the skin making sure we get sufficient product around the nose, eyelids, into the ears and even between the toes. For around the eyes we spray it into our hands and rub it around the eyes.
So far we haven't had any fungus since doing this. We also spray everything that went to the show, including our shoes. I keep a can inside my truck and spray my shoes and hands anytime I've been somewhere that I think could possibly have fungus, bacteria or viruses that I wouldn't want to bring home.
It does treat fungus. As a side note, it works for athletes foot fungus, too. (Thanks OG!)