I'm an hypnotist and yes, it works.
However, approximatively 10% of people are able to go easy deep enough to accept such suggestions. You're lucky to be part of them.
I have one good ABDL friend that has this chance and we play sometimes with that. One funny example: each time she drinks something she absolutely need to go to the potty in the 5 minutes if she's not padded! She can go every 5 minutes! Another day she wasn't padded and seated in my couch. I tried to make her let go but the beauty of the brain is that she was unable to do it in the couch (inconscious brain didn't accept to ruin my couch). She was desperated (due to suggestions) but unable. So I asked her to go on the balcony to see the view and at the second she put her feet outside, everything went out!!! was a great fun, she couldn't stop at all.
I do this only for the fun. I'm a hypnotist for fun (shows, based on hypnosis phenomenons) and also a hypnotherapist. But for the therapy, I'm sorry, don't ask to become incontinent as this is against the ethic and I don't do that. (Anyway, I only do it in French, my english is not good enough to ensure good results in english).