IMO in addition to physical pain, psychological pain should be considered as well, so I don't consider methods that are potentally frightening and violent such as firearms, jumping from height, vehicle and train accidents, and drop hanging to be "painless", and definitely not peaceful. The inert gas exit bag is the only method that I've found that's accessible to me, painless, peaceful, quick, not a danger to anyone else, and reliable. I read that Nembutal is the "gold standard" of peaceful, painless, quick and reliable, but it is illegal and too difficult to obtain for me to consider. I'm not convinced SN is painless, and without a recommended antiemetic, I fear I wouldn't be able to keep enough of it down and drink additional doses if neccessary.