When I set my mini wsm up for a cook I fill up my chimney with unlit charcoal which is about 60 unlit briquettes of Stubb's. I take that chimney and spread them around the charcoal grate. I take 15 briquettes out of the middle and light them in the chimney. I bring it up to about 215-220 with both vents wide open. I then shut down the bottom vent all the way and let my IQ110 go to work maintaining 225 for the durration of the cook. When up to temp I add 1 chunk of whatever wood I intend to use.
Today I did this same process. I let it get to temps. cooked some ribs using a 3-2-1 method and closed down all of the airflow to snuff out the remaining coals. After it was all put out I have plenty of briquettes left yet to be burned. One day I need to start it up and see how long I can go before adding more coals to maintain temps. A bag of charcoal will last a long time.