What the smoking does is slows the rate of heat transfer into the mold. It doesn't hang around for long on the mold surfaces, though, so my guess is it just gets you dropping good bullets from a cold(er) mold faster. By the time the smoke is gone your mold should be up to temp.
I cast .454 round balls using Lee's two-cavity mold. I have no problems casting out in my garage, though it's seldom below 50 out there. I cast pure lead at about 750 degrees F.