I use the entire 16# bag of KBB. That will get me a 12 hour cook, weather dependent, of course. I put the entire bag in the fire ring. Then I put 8 briquette in the chimney and lite just those (no lighter fluid!!!! ha ha ha ha).
When they're hot, I spread those 8 across the massive mound of charcoal.
Put something in the water pan. Whether it's water or sand, or whatever....
Use foil, it makes clean up MUCH easier.
Open the top vent 100%
Open the bottom vents the width of a bamboo skewer. Let the fire do its thing for an hour before you put the meat on. From there, adjust the temps as needed with the bottom vents.
Make sure the door fits as tight as possible, they aren't perfect.
If you're not using the bottom grate, just leave it out of the smoker altogether. It's one less thing that needs to be cleaned up.