Might want to change the title to "tulpas", "tulpae" is a nonsense word that means nothing. You can do it yourself as far as I know, but I can change it to you as well.
Lessening pain, definitely. Of course it's something that I was able to learn myself too. Sometimes having a simple tulpa is pretty useful, when his advice is "just do it, I could do it, you can do it too". And in the end, it's nothing more complicated than that. It's just about ignoring the pain, though we haven't exactly tried it with anything too painful and it does take some effort to do it. Maybe with practice, it would become really easy?
There's been reports of people saying their tulpa/s have given them the feeling of high if they have experienced it before in their lives. Does anything actually happen? Hard to say, no one's tested that. The mind is one hell of a drug though, you definitely can mimic a lot with your imagination and make it seem real. Just be careful and don't be stupid about it.
Can't some people give themselves an adenaline rush anyways? Maybe I'm just thinking of something else, but eh. Kind of repeating what I said before, but you don't need a tulpa for this kind of stuff. Again, can't say if anything is actually changed when it comes to the chemistry because no one has tried, but if you have enough willpower and really think it will happen, you can do it. Placebo is a real thing and all that. Many people had the thoughts that tulpas have some innate powers of being able to do things in the brain, but really, you are the same. It's just you doubting yourself hindering you there.
As for Koomer, I'd say he didn't start this entirely sane already and the schizophrenia-like stuff had been posted even before of the whole drug thing, unless he had started the drugs before and didn't just mention them, but did mention the other dudes. At that point he was calling them tulpas, though, but that was posted in a place that as far as I can say, is gone now. Afraid you either gotta trust my word/bad memory, or ignore this as crazy ramblings.