find a friend with a car if you sketched about going outside. Smoking in a dorm, however convenient, is really dumb. I have a few friends who were kicked off campus for it last year (idk how strict your school is).
However, if you must, be super careful. RA's can smell it from the hall, from an adjacent window, or from a window above you. I would recommend putting the towel down, covering the smoke alarm, spaying axe or something right by your door, even a bit outside, and then getting a fan right in the window. Use a bowl, and keep it like 6 inches away from the fan at all times. Who's ever turn it goes to the fan, and blows the hit right into the fan.
Also, if you build a spoof (dryer sheets , tp, towels, or whatever in a soda bottle, you should be ok. Always be careful when you do it.