When you turn your fan off, do you just turn the fan all the way down??? Or do you turn the system OFF.
I have success w/ keeping the smoke out when I turn the system off, which is different from turning the fan all the way down. If I just turned the fan all the way down, the smoke would still come in, because the fan is not off, it's just running at a very low speed.
If you don't have the ability to turn the system off, recirc is going to be your only option. As long as you have it on "vent" with AC OFF the AC will not kick on, if that's what you are worried about. If you have it on Heat, or Defrost, the AC pump will still kick on and off....Well, it does on my '00. Maybe someone w/ an '04 can chime in here, since I don't have one to clarify.
Good luck,