I think the less preparation, apparatus and discomfort involved are factors that can help lessen the instinct.
I agree 50%. I've flubbed it several times, but while at first I thought it was due to the set up of the apparatus (eb/N2), a lot of it is simply the time it takes to get my farewell notes set up, notifications ready on the delayed email, etc. So it isn't so much the method or the apparatus as it is my inability to be impulsive.
But I live alone and can get my apparatus set up at any time without worrying about someone walking in and stopping me. If you do need to take the time to get everything set up, then the complexity of your method would contribute to that delay and could make the attempt less successful.
I used to pooh-pooh the stats that say guns make suicides more likely because they increase the ability to ctb impulsively, but it turns out the idea is sound: if I didn't care about a note, or having the right person find me, or leaving a minimally traumatizing corpse for my family, I could walk 15 feet to my gun locker and be dead in a few seconds. A method is
a lot more likely to succeed if it can be attempted impulsively.
So to keep with the OP of this thread, the less conducive the method is to spontaneity, the more I would recommend
against that method regardless of how otherwise peaceful or effective it might be. It could lead to "operator error" rather than method failure.