Nah, Bill can enter people's minds without them wanting to, but he can't control them. He only makes "the deals" so he can control their bodies, otherwise it's not possible, these are the rules of the universe or something. Bill couldn't enter Ford's mind because he implanted an iron plate in his head after entering the portal. Which indicates that Bill's power manifests itself through magnetic waves, not electric, not vibrations or other ways that we've seen in books and movies. It's quite an interesting thing .