Like Cmayna I have had great success with the Slow-n-Sear. Before getting it I used the matching Weber smoking charcoal holders that are intended to sit either side of the meat.
Cmayna mentioned something I found important and want to be sure others understand. The foil on the lower grate seals off air flow through that grate except for under the SnS. Therefore, the air coming in the lower vent ports must all go through the SnS. The lower port is only open maybe a 1/4" max for each of the three slots and the top air control is only open 1/4 . Air control is easy and makes for consistent temp control. Last time I set it up I got three hours steady 250 with steady TBS from the pecan chunks.
The other trick is to use four large alligator clips to hold the lid tight to the base to stop air leakage.
I ordered a sns and its supposed to be here friday. Untill now ive always used the minion setup with a large foil pan under the meat.Good to know about the foil on the charcoal grate. Cmayna do you fill the water resevoir