Looks like a lot of people responded to this and you don't really need my input here. All I can tell you is what works for me. The kettle is actually pretty good at holding temps, but it's not set it and forget it. You have to keep an eye on it. Even if its like every 30 min or so. Small adjustments make a big difference. I do not have a slow n sear. I feel like its a lot of money to spend on something that doesn't really do a whole lot. I use a couple fire bricks that I wall off about a 3rd or so of the way on the grill. Then if for instance its just ribs, and I know Im going to open the grill in 2 or 3 hour to wrap anyway, I do the snake method on the short side of the grill. I also foil the other side of the charcoal grate, so theres no air flow underneath the food, and it also keeps the bowl clean. If its something that will take longer like a pork butt or a brisket, I use the same method, but instead of a snake, I just use a full unlit chimneys worth of charcoal. I also use briquettes because they do not burn as hot, however, if you are careful I don't see why lump would not work. I always start with like 6 lit pieces of charcoal at one end and the vents top and bottom wide open. When I am within like 66% of my target temp, I put my food on and close the lid as fast as possible. I then cut the bottom vent down to the first dot, on the one touch, which is the round part of the P on the vents. If you have the old school vents, then its to about 1/3 open. I leave the top vents open, over the food. When it gets to within 20% of the target temp, I cut my top vents to like a quarter of the way open and then I watch it. The temp should gradually level out to around your target, and you should be able to fine tune with minimal movement of the top vent. It is important NOT to overshoot your target temp, because getting it to come back down is a pain in the butt! That being said, if and when you open the lid, your temps will spike. As long as its not more than a minute or 2, that's ok. You'll put the lid on, your temp will climb to over target. don't freak out. It will come back down within like 20 min or so. 20 min at 310F isn't going to make a whole lot of difference on a rack of ribs that is going to cook at 250 for 4 hours anyway, much less something that can take more more heat for much longer like Brisket for instance.
Also, I absolutely love smoking on the kettle. I don't have a WSM, but I do have a drum smoker, and I like the kettle way better. It's easy to use, and it's pretty good at holding temps.
