I use a S'nS and a TTT. For reverse-searing steaks, I run the bottom vent at 1/2, TTT on the top. Hold 225-230 with lots of smoke. Key thing is to not overdo lit charcoal. For the sear, open the bottom, remove the lid, and blast the coals with the BBQ Dragon until you've got big, open flame.
The TTT is a great way to maintain temperature, though I rarely use the Weber for longer cooks. I find an insulated smoker holds temperature more consistently.