I studied hypnosis for a while (out of an interest in mentalism, and not so much the medical aspects), and this is pretty much what every hypnosis book and course preached.
Basically, pick a simple metaphor and state everything in positive terms.
You've probably heard the trope "Don't think of a pink elephant" which of course forces you to think of a pink elephant. Instead you can "notice how all the elephants in your mind are grey." It's the same reason it's not possible to tell Brain, your dog, "Don't Sit!" once you've conditioned them to sit upon hearing that command.
The only books I bought on the subject are specifically about the mentalism variety, which probably isn't really what you want. I also got a book on the medical variety of hypnosis, but it is old and no longer published (I actually met the author, which is how I got it).
However, for videos I highly recommend a fellow by the name of Igor Ledochowski. The main reason is that he seems to have studied the subject more in-depth than anyone else I've seen, and has come up with some really useful models that explain very well what each part of the process is for, and variations on how they can be applied, what to expect, etc. Most practitioners seem heavily focused on a single method (and nearly always only the earliest known methods which are outdated by today's standards).
Although I bought some of Igor's stuff quite a long time ago, the reality is that the videos he released on Youtube pretty much cover everything he talks about. Forget the hand-stuck type stuff and search out his model discussions (complete with whiteboard), since they get far more into behaviour and process.
Basically, pick a simple metaphor and state everything in positive terms.
You've probably heard the trope "Don't think of a pink elephant" which of course forces you to think of a pink elephant. Instead you can "notice how all the elephants in your mind are grey." It's the same reason it's not possible to tell Brain, your dog, "Don't Sit!" once you've conditioned them to sit upon hearing that command.