Does Tom give techniques on HOW to switch data streams?
Essentially intent, focus, meditation, getting rid of beliefs but in the instance you're referring to, it becomes natural after practicing it so many times.
Just like if you had an OBE recently, you are temporarily more able to remember how to get into that state that induced the OBE. It has been chemically stored in your memory and you are able to recall that state easier. Over many, many instances of parsing data-streams, I imagine neuro-plasticity takes effect and it becomes like a second nature.