I would try subtlety first. If you get the opportunity, strike up a mild, light, political conversation, or even about how amazing technology is and how ‘in the old days, you’d have to make your own soap.’ Stuff like that seems to quickly interest the prepared and bore the brainwashed. Very subtle hints are how I discover those who are brainwashed and those who are not. Perhaps I have a knack for picking them out, but I seem to discover like-minded people almost immediately. If they seem to respond positively… talk about a topic slightly closer to prepping… if they turn away, immediately drop that subject and NEVER mention anything again. Opsec is important.
Hope this helps!