Hate to bring up a old thread but I have some observations to add
the first is about having spare charcoal ready to throw on, I do a bit of dutch oven cooking and when you learn to do that you need to have a few things, either a supply of burning charcoal to add when needed or a propane burner to light coal. No not one of those huge weed burners from Harbor Freight, but a small hand held system you can light a few coals fast with, like a plumber uses, except using propane and not map gas. (map gas not recommended around food) A couple minutes with the torch and lighting charcoal is fast.
Second, try experimenting with foil on the bottom grate, not under the coals but where the coals are not, that way the air coming in is forced to go up through the coals, not the area you have the indirect grilling going on. PS you will be amazed at the smoke roll you will get this way. (I got this idea because when you see the big tin water holder placed in the bottom, it basicall blocks air from coming up that way, so I experimented and decided lining the floor of the unit except under coals can do some positive stuff,)
another point is to use the one touch to clear the underside of the coal grate, as charcoal burns it drops ash and that can get in the way of air getting to the bottom of the coals.
Hope all of this helps