I'm not ADHD, but I've had the exact same issues as you do. Frankly, it's enough to drive a guy a little nuts seeing how easily other people can slip into trance. XD
I haven't really done all that much in the way of hypnosis since I've heard this tip, but I once heard the suggestion that you try listening to the file as though you are already in trance. Just go along with whatever it says, and don't think too hard on it. It's kind of paradoxical, but you need to listen, without really letting your mind tune in. Try thinking the words of the audio alongside the audio, and do as it suggests. Like a play, and you're acting out the script.
Like I said before, I haven't done it too much since I heard that tip, but I managed to get a couple decent trances with it.
Listening to mental blockage cleaning binaural beats can also help, if you listen anywhere from 10 minutes to an hour of them before trance. If you keep it up, eventually your resistance will begin to be weathered away. ESPECIALLY if you listen to them consistently.
It's also just a matter of practice. On days that you don't listen to files, try meditating. Trance and meditation are pretty similar, and so learning how to do one can work with the other. It's an acquired skill; much like your ability to play a certain sport, there's natural aptitude and acquired skill that apply more or less equally to your ability to do well. And if you don't have much aptitude... well, that doesn't mean it's impossible. You just have to practice a lot more for it.
You might want to take the hypnotic suggestibility test too. Just look it up on Google or whatever other search platform you use. There's a sort of quiz to take, and at the end it tells you the way you usually process information. It's not so much a way to trance better as a way to *figure out* what helps you trance better.
Last I used that quiz, I was mostly an Inferring Suggestible. For Inferring Suggestibles, misdirection and inferences work better for trance than direct commands. Technically, we have the short end of the proverbial hypnosis stick, since most hypnosis files aren't quite suited for us. Though the trances Inferring Suggestibles can get can be quite strong when they do occur. The 'prime' subject is a perfect 50-50 split.
EDIT: I forgot to mention, that one of the most important things in hypnosis is TRUST. You need to TRUST your hypnotist in order to obtain any sort of meaningful trance. It's like a mental trust fall. If you don't think the person who's going to catch you will actually do so, would you even want to take the risk? The same applies to hypnosis, pretty much.
Anyway, those are all the tips and suggestions that I have for you. Hopefully some of these help out!
