Auto air purifier from Famous

dunno about all the windows down, but I drop the drivers side window about an inch to inch and half, then put the fan on, blowing down at my feet (fan, NOT the A/C) - it works by negative pressure - the smoke gets sucked out the window.

I smoke in my Dakota (Baby) everyday on the way home.

Also, if you don't have them, a great addition is the ventvisors on the outside so you can drive with your window down in the rain.