So you summon all weirdos, or at least most of them, get them high on magic and stuff and call it a festival.
You give them the set and setting to externalize their inner world, which turns into a feedback loop with the whole set and setting business, and pretty goddamn quick you turn up with something that looks like a collective subconscious. A place where what you see with your eyes open what you usually see with your eyes closed.
Now doesn't that sound like a good place to contact the Dreaming?
Oh, and they also sacrifice a YETZIRATAN.