Well, besides that, possession doesn't really manifest itself in ways that make you suddenly become a well-known entertainer like these guys.
It more resembles a fragmentation of the persona and association with characteristics that appear to be from outside of the Self... from what I understand...
I am familiar with certain people who perform invocations, basically drawing a persona (demon, daemon, god, angel, whatever) into themselves, which functions like possession. Some of them are whackjobs to begin with and so they can just imagine all sorts of nutty things, but others are quite intelligent, educated, otherwise rational persons.
From what I gather, "daemons" would likely be quite put off to be put to the task of guiding the possessed to perform stage magic. But then again, I'm not very familiar with Goetia either.