Apparently the Catholic Church has a shortage of Exorcists and has a sort of 2 day seminar for priests to learn how to do it.
According to Bishop Thomas Paprocki of Springfield, the signs of possession include:
“The person has some knowledge of hidden things that they’re telling you things about yourself or about the future that nobody else could possibly know,” he said.
Among other signs, he said, is a person having an aversion to things that are holy.
“So saying prayers over them or sprinkling them with holy water and getting a very violent reaction,” Paprocki said.
The first bit seems to be describing Catholic Priests and the last bit sounds like me.