Again. It's damn there impossible to keep a consistent, even, constant temperature with a "grill". I've seen a method where you close all the holes in the grill and add a fan and thermometer to get the desired effect, but it's much easier to use a smoker which was built for the purpose of creating that kind of cooking environment.
Yes you can use the indirect heat method that you posted, but it won't be truly smoked food. You can't use that method with any consistancy when cooking things that take 4-8 even 12 hours like pork shoulder, beef brisket, smoked turkey, etc
As for the gas/pellet smokers, they are a good substitute but nothing beats the real thing.