I would not go blocking off vents and such on a gas grill. Looking for trouble. Especially to an inexperienced griller
In spades, Larry! Blocking vents can literally choke off needed air and prevent the gas from burning. When air is introduced again, the collected gas can suddenly ignite and you have a gas explosion. Ask me how I know.
I said above that I have tried for many years to get true smoking from a gas grill. With an earlier 3 burner E/W config Genesis, I installed an adjustable band across the rear main vent (opening between the hood and the base). It worked, but when the air escape was limited sufficiently, the already lit burner(s) were snuffed out when the lid was closed and when I lifted the hood to check out the problem WHOOM! It actually happened twice before I figured out what was happening. Fortunately nothing but singed eyebrows. I removed that "damper" and now will never block that main "vent". These grills were designed for a purpose and trying to modify them can be risky
Check my past posts and you will find that I still try to get the best "smoke" results I can from a gasser. All the Weber gas grills come with hoods that do not "seal" around the firebox which allows any smoke to escape from all sides. I had a cyber friend on another now-defunct forum who had family that worked for one of the meat prep companies (forget which, Armor?). He said that true smoking requires not only smoke, but pressure (look at how a WSM operates vs a grill -- especially a gas grill). Smokers are low heat, smoldering type fire. You can damp the vents to get the smoke and temp you want, but almost everyone says to keep the upper vent wide open (barrel smokers excepted). I've tried many ways to control the smoke in a gas grill including adding woodstove gasket around the hood to block smoke escape from front and sides (that is successful and has not been an issue as long as the rear "vent" is left unobstructed. (The issue above occurred when implementing both gasket and damper.) Having my upper grate available, I've laid baking sheets over the lower grates to restrict and direct heat and smoke up from front to back over the meat and out the rear, wood and even charcoal chunks resting on a plate over the flame tamers, a tube with wood pellets and set the minimum heat possible on the lower BTU sear burner. I got good smoke and decent smoke flavor on the brisket, ribs, butt or whatever I was trying to smoke, but I never accomplished a true "smoked meat" with a smoke ring. I still do it at times, but not with any expectation of truly getting smoked meat from my Genesis. It's why I ended up getting the WSM 14.5. If anyone has further suggestions, I'm open to advice.