Cayce was not lucid in his trance readings and had no idea what he had said in them. Where did you get the idea that it was not "his soul" speaking in his readings? EC himself described this trances as involving OBE in which he traveled to the Akashic records. On the whole pretty much like vanilla near death experiences except he was not conscious. What abilities! He was the classic psychic all horn and no beef, with he followers clinging to the few things he got right and ignoring the much more numerous failures. As for learning to do what he did (assuming it was real) why not ask Carla L. Ruechert who is doing the same thing and is still alive?
"There is only one God and his name is Death.
And there is only one thing we say to death "not today"
- Syrio Forel