To clarify, I'm only talking about cleansing your physical 3D bodily form, that is all which is needed to remain. Those who can't do that will have their body "deleted" and recreated at the moment the pressure is levelled out and the gate opened, but there will be a physical process before that. I can't tell in what form, according to what Yuuka said earlier the lyran involvement may result in a very orderly transfer with no large timeline crash, i.e. no WW3 or buildings crashing into each other. But there could still be things like energy and consumer goods shortages worldwide as part of the cleansing process, putting you on a forced diet. That's one interpretation of what it means to be forcible cleansed.

I don't do most of my yoga and qi gong simply for this purpose, it's one aspect included when working on the other layers. If you're only doing the physical cleansing you theoretically don't need to bother with anything esoteric at all. Ascetics could probably do the job (fasting and abstaining from media consumption for example).