Go to Home Depot or Lowe's and by 5-6 lbs of duct seal compound. They're like $2.50-3 each and can be found in the electrical section.
When you get them home, unwrap the block and work it around in your hands so it's more pliable. Or you can just let it sit in the sun for an hour to soften it up. Then take a rolling pin or squash it out with your foot so it's about 1/8" thick or so. A 1# block should cover at least 1 sqft. It will probably look like a big pancake when you're done.
Apply one pancake to the center of the door panel and tap test it for resonance. One is probably all you need, but two of them probably won't hurt.
At this point, you're probably done. Forget the "deadener'...it's a product contrived by the Illuminate in cahoots the petrol industry to control the feeble minds of loud-music-seeking youth. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif