Dique,
Normally depends on what you are using for.. I presume u mean for the door. The best is 1 layer for the metal and 1 for the plastic panel but that aint so cheap... need at least 2 layers for the door.
Normally you stick aroudn the speaker area and directly behind the speaker area. Any elftovers you stick at the metal and the panel to make it resonate less.
Garry,
For Satria Doors, as its bigger than a Wira's... you will need about 1.5 pieces of DE if you are going to stick on the whole metal piece.