What is automatic writing? For some it is the ability to take pen or pencil in hand, put pen to paper and have the pen move and spell words without conscious effort by the user. This is similar to a writing technique used by Ruth Montgomery with a typewriter. The actual conscious writing effort is supposedly produced by an entity from the other side. Hopefully, someone nice who has passed on or a higher entity. I’ve attempted this technique several times, but to no avail. This video for me only produced scribbles on the page. I certainly wouldn’t recommend this to anyone to play around with casually, as in the “hands” of someone not prepared properly could bring on all manner of chaos.

I do have a technique for automatic writing that doesn’t involve the loss of control of one’s hand. It involves pen and paper and just writing down whatever pops into one’s head. Some may call this free form writing, and most writers use this technique only until the conscious brain takes over, a warm up technique as it were. However, if done consistently free form writing can lead to some pretty fascinating information.
Some books on automatic writing include:

How to Do Automatic Writing by Edain McCoy

The Ghost Writer Automatic Writing Kit: Messages from Beyond and Magic from Within