I genuinely dislike guns, and I hope that I'll eventually find an SN supplier so I won't need to consider taking this route to CTB.
With SN, I'd just pass out after 20 minutes and die peacefully. My skin would turn blue, but it shouldn't be a grotesque sight for whomever finds me.
Honestly, my backup plan if SN falls through is to select a nearby lake for drowning or death by exposure (i.e. hypothermia). I was not a violent person in life, and I do not want my life taken by an instrument of violence.