Ouch, tough door to work with. Definitely use at minimum one layer on the inner part of the door. Put some closed cell foam over it (like Overkill from secondk skin). Put at least one layer of deadener on the out part of the door. To cover up the holes, it will will take time but will make an improvement. You can get some sheet metal screw it into the door and then put deadener over the sheet metal. To ensure less rattle, put Rattle Pad (from SS as well) between the door panel and the door. It's easiest to feed any wires through the Rattle Pad and stick it onto the door by using velcro, so that if you have to remove it, it would be easy.
As Ed Lester mentioned, you can also you Spectrum. Great stuff but you will need a few layers. 3 of those layers at minimum. I recommend spraying it, but you would need to use their spray gun since it's thick. Or you can use a regular one by mixing it with a little bit of water and it will spray easier, but you will need more coats since you diluted it with water. You can always paint it on, but it is time consuming. If you want, you can get the Sludge Activator and it makes it THICK. You can spread that with a putty knife of something similar, but I just used my hand (with a glove of course).
Personally, the Damplifier (or Dynamat Xtreme in your case) will be quicker to do since you would need several layers of of the Spectrum and you must let it sit and dry. I hope you have success with the Dynamat Xtreme. I needed some deadener and I bought a door kit for 15 bucks, totally not worth it. It was thinner than Damplifier (not Damplifier Pro) and the adhesion for the Damplifier was better. Once on the Dynamat did stick on, but it had to be rolled on hard, just my experience, yours may be different. I've messed with several different brands of Deadener and I'm glad someone had mentioned Second Skin to me. It's the best stuff I've used.
