In my experience, less charcoal doesn't really provide lower temps. I've had good luck dialing in temps by putting small bits of aluminum foil around the rebar. I'll play around with loosely wrapping a couple of the holes, usually on opposite sides of the barrel. You can crimp the foil a little tighter to reduce airflow or pull the foil away from the hole to get more airflow until you dial in the temp your want. pmillen is correct, you don't want to choke down the airflow too much, because you run the risk of incomplete charcoal combustion which makes for acrid tasting smoke. I've had luck dialing in clean smoke down to about 250 deg F. I never mess with the bottom vent. Your mileage may vary, of course, but half the fun is the learning curve on this cooker! Good luck and enjoy.