That is the way to do it. Always leave the top vent open, closing it will simply keep the smoke and heat trapped inside, and the fire will not burn well. Creosote will follow and you do not want creosote. I inadvertently left the top vent closed on a cook, it was dark outside, and I couldn't figure out why my temps weren't rising. Finally noticed the vent was closed. Opened it up and all was well. At the end of the cook I noticed that the inside of the dome had all this gooey stuff stuck to it. Creosote. Very tough to clean of. Fortunately the small amount of beef jerky survived, and was not too bitter. Lesson learned.