I am about to install my system and I want to sound deaden as much as I can. I am going to concentrate my efforts on the doors and the rear wall (pickup truck). I was curious about a couple of things though, when you guys deaden your doors do you put a layer(s) on the metal part of the door and the plastic doorskin or just the metal? Also, can anyone give me a link to thorough and detailed instructions on the sound deadening process? Most places I've found spend a lot of time explaining prep but don't go into much more detail. Thanks