Best particle settings for fog

Hi Everyone,

I am creating a creepy Halloween themed scavenger hunt. I started playing around with particles to create fog but not having much success. Does anyone have a good recommendation for settings to make a creepy ground fog effect using particle system?
Thanks!

Which particle system are you using? The one in Studio?

Yes. I am making progress with a slow emitter speed and forces using a highly transparent sprite that I made in photoshop.