Can everyone be hypnotized?
Hypnosis is the ability to enter the trance state of consciousness at will. Given that trance is a naturally occurring state of consciousness all hypnosis is in fact self hypnosis. The hypnotherapist is a guide who teaches the subject to enter trance at will. Given enough flexibility of the hypnotherapist everyone can be guided into trance that is to say be hypnotized.
Most people can learn to enter the trance state quickly. Some people take longer time to learn the skill. Milton Erickson claimed he had managed to hypnotize almost everyone and there were a few he was still working on.
In my own practice, I have not yet met anyone who wanted to be hypnotized that I have not managed to help enter the trance state. In my system of hypnotherapy we believe that there are no resistant clients but hypnotherapists who are not flexible enough. A flexible hypnotherapist knows many different ways of teaching people to hypnotize themselves. Thus you can never be too rich, too slim or know too many ways of inducing hypnosis.
Another important thing to know about hypnotherapy is that even a light trance is sufficient to produce hypnotic change. I find the hypnotic pretalk during which one explains what hypnosis is and gets rid of misconceptions about hypnosis the most important aspect of guiding people into trance.