1) Get the friend re-oriented with the real world. Newspapers, current events, current music, latest electronic gadgets - whatever.
2) Get the friend re-oriented with real time. How old he/she is, retirement plans (none?!?), medical, plans for children.... he's not 23 anymore, right? Latest scientific, psychological and other advances. Hubbard 1950s tech doesn't cut it - and finding out what's out there makes it look all the more stupid.
3) Give the friend stability outside the Sea Org. Be the friend who he knows he can count on if/when it all falls apart and the one he can talk to who is trustworthy because you will never repeat what he says in confidence.
4) Make sure he knows the emeter is not unbeatable. Best to tell him stories of others who have beaten the emeter in a joking, lighthearted way - so he knows he never has to tell Scn about his conversations with you.
5) Tell him your wins in real life and the real life changes that ACTUALLY occurred that made you happier, more successful, more loved and lovable.
6) Make sure he understands the idea of everyone's path belonging to themselves and that there is no pre-made path to personal enlightenment for anyone. Eternity cannot be bought or sold. The Catholic church already tried that (and others before that).
THEN, if you can get through all the above, it might be time to show him some real info, a little at a time, about COS and the rest. He has to realise he has personal goals of his own, first - and that Hubbard's or COS's goals are not his.