My faith states that exorcism is pretty a straightforward deal. "Sir, I must insist by the powers that be, namely Christ Jesus our Lord and Master, Do leave the premises."
Makes for bad cinema but also bad camp fire stories. This stuff ain't no joke, if God wanted you there, it was for your witness and experience, not so you can tell 'scar-y' stories around a fire. Shit ain't spectacle, and one should never want to be in such a position to say "I've seen the demons rush out" or wish to know too much of the affair. Theirs also something about spirit return and entrenchment, but that wouldn't make a happy ending. Also consider the fact that people are naturally dicks even after such hard trauma. Unless... well, you know the rest of the Gospel.
My $0.02, YMMV