I assume you've read my post from January reviewing the entire method:
https://sanctioned-suicide.net/threads/inert-gas-cylinder-regulator-general-refresher-summary.30657/
You're making a common error often seen on this forum: confusing the two different types of Survival Instinct.
The first type is a function of the autonomic nervous system and includes things like hypercapnia (a physical reflex to the the build-up of carbon dioxide) that can include anything from wild, panicked physical actions to hiccups or yawning. The startle reflex, coughing, the mammalian diving reflex, jerking your hand away from a hot stove are all other examples.
These are deep-seated, instinctual, uncontrollable, evolutionary adaptations that are indelibly programmed in our brain stems.
The brain has no instinctive response to breathing inert gas; it just thinks you're breathing air, until you painlessly and quickly pass-out and die.
So what you're worried about is the second type of survival instinct. It's psychological. But it's very powerful and very
real, perhaps just as powerful and real as any physically instinctual brain stem reflex. And just as difficult to control.
Some people call it the will to live; others self-preservation, fear of dying, a primitive force that clings to life. On and on. Religious folks have their take on it, social activists have their take, poets theirs, even politicians weigh in, unfortunately.
Let's just say that that taking one's own life, for most people, is a scary proposition!
And as with anything that scares us, we react.
You're going to have this same psychological/emotional survival instinct kick in no matter what method you choose. Standing at the edge of a high place or your finger on the trigger or a rope around your neck or your hand around a glass of SN--you'll have that moment of doubt and fear. When my time comes so will I. I wish I knew the answer, but I don't.
The Exit Bag & Inert Gas method involves about 10 to 15 seconds before unconsciousness. Death follows in a few minutes. What you're saying is that you need to find something that gives you less time to think, but there is no such thing. No matter what the method, you will have that moment...that moment at the brink.