The amount of rattling is kind of directly proportional to the thickness of the metal sheet of the doors and rear shelf. since the front doors are longer then the rear doors, the rattling is felt more on the front doors. the thinner the metal sheet, the more heat will also be felt on the other side.
So for the optimum results for the floor, rear seat metal sheet (in case of sedans) and front firewall, the carpet is removed the metal floor cleaned. then the dampening sheets are applied to the floor, rear metal sheet and firefall to help reduce the road noise and engine noise. then comes the "NAMDA" as what its known here to further help in reducing the heat and somewhat the sound aswell. the carpet is then placed ontop.
As for the doors, the dampening sheet is applied to both the inner and outer metal sheets of the doors. this makes the door as an enclosure, sealing off any holes. the only point to take care of is not to block the holes that let the moisture or water drain from inside the the door.