A good method is to warn them of how long and complicated it is, and that under no circumstances should any of them try to speedrun the thing, out of worries for their health.

If they're headstrong enough, they'll take it as a challenge.

Take the risk on scaring them. Those that know the risks will hopefully be ready for the journey ahead.

Also, make sure to send those interested a link to the unofficial homestuck collection, to make it easier to take the first step.