I had spent a month or so preparing it. I bought the tubing I needed, a tank of helium, and a whole load of duct tape for security reasons.
I heated up the end of the tube and connected it to the tank, and stuck the other end of the tube to the inside of the bag I used, which was elasticated. I placed the bag on my head and let it fill up with helium, before pulling it down over my head. It was painless, and I was going faint, but I just wouldn't pass out. I tried three more times in the same night but I must have done something wrong.
Now that I think about it, I really rushed it far too much. I didn't scrunch up the bag to get rid of the air in it, nor did I use a regulator. Also, like the OP of the megathread said, helium isn't that reliable these days, so that could've also been the issue. I'm probably going to try again since it wasn't painful at all, but I'll take even more time. I had tried to ctb four times in that one month and I wasn't in a state of mind where I could think clearly.