I have seen a Criss Angel Metamorphosis from his Stage days where a blanket of fog is dropped from overhead.
I am sure if you serach YouTube or even Penguin Forum, you can find it.
I had a problem because it takes too long for the fog to clear, thus adding time to the change. Crissy also did a change in Season 2 of his TV show using Flash Pots. (They over did it though an the assistant was burned).
I agree. And yes that can be found on youtube. If you watch it I think you'll find that the fog really slows down the illusion. You might also want to be careful with using extremely bright lights. Here is why:
-If the setting has been in low light for a while and you suddenly flash bright lights in the crowds eyes it will actually hurt their eyes.
-If you temporarily blind the crowd they won't be able to see because they'll have those dark spots from being blinded.
I would recommend you test these things on yourself first.