Everyone who can follow instructions can benefit from hypnosis. It is simply about following the suggestions. If you can listen and follow suggestions, you can be hypnotised. Which means you can achieve successful results with hypnosis.
There is no special feeling of whether or not you are hypnotized. Hypnosis is experienced as a state of being deeply relaxed. In fact, if you wanted to compare hypnosis to anything, the closest you could get is when you are extremely relaxed early in the morning just waking up or late at night just drifting off into sleep where you are not really sure if you are awake or sleeping.
Hypnosis is perfectly safe. No one has ever been hurt using hypnosis. When you are in the relaxed state of hypnosis you are still awake and aware of everything that is occurring. You are still in control of what you do and don't do. You cannot be made to do anything you don't want to do. You will remember everything that occurs during the session and you can't get 'stuck' in hypnosis just like you can't get stuck in a relaxed state.
You have an unconscious and conscious mind. Your unconscious mind is the one that drives your life. It does everything you don't think about - for example all your habits that you just automatically do without having to think about them. And the conscious mind is the part of your mind that thinks, and makes choices, and decides what it is you do and don't want to do.
The problem is that your unconscious mind will take over when you are not consciously thinking about what you're doing. For example, have you ever driven to your destination and realised you don't remember much of the drive? This is because you were likely daydreaming about other things with your conscious mind, and so your unconscious mind took over driving the car out of habit.
What hypnosis does is it utilizes this state of deep relaxation where your unconscious mind is open to directly absorbing new beliefs, thoughts and habits. This means that when you are not consciously thinking about quitting, your unconscious mind takes over and works for you to be a non-smoker. You naturally and automatically think and behave as a non-smoker.
There is now no 'battle' of will-power between your conscious mind wanting to stop smoking and your unconscious mind still stuck in the habit of smoking.