I don't think hypnosis can be counted as an 'extreme' method, seems to be perfectly fine and some people here on dreamviews are using it to help in lucid dreaming as far as i know, and also technically mantras that we do for lucid dreaming are also can be somewhat counted as an form of self-hypnosis on the some level, i think.
And as far as the 'extreme' methods i used, i only used some sleep deprivation when i was starting out and didn't know much about lucid dreaming, unsuccessfully to say.