What I've been doing (I'm a newb too, been fixed +/-6 weeks) is doing a little skid on each revolution going down a hill to scrub some speed and keep from becoming an out of control freight train. I just wait till my strong foot(left for me) is forward and skid a bit. Then, I let the cranks go around again till my left foot gets to the front. Skid again. Repeat ad nauseum or till you get to the bottom, whichever comes first.
Your mileage may vary.
BTW I'm running 52X21