There are two keys to becoming a trance medium: surrender and vulnerability.
Most people would rather keep up the fight than surrender. And, in our society we have developed countless ways to remain invulnerable: locked doors, closed minds, television broadcasts that reinforce that we should fear one another.
Surrender, as it pertains to mediumship, is about surrendering to the other perspectives, whether you believe them or not. Dr. Peebles speaks to people from all walks of life, from all around the world, on a variety of topics (some of which I am not even familiar with). If I happen to overhear him speaking to someone I have never met, and he says, "When you were a child and were visited by extraterrestrials..." I have to surrender and allow for those words to come through. I could step into a place of fear and resistance thinking, "I don't even know this person! Extraterrestrials? What if Dr. Peebles is wrong?"
That's simply a thought that I cannot entertain, or I will block information from coming through.