I only use spray stuff - undercoating, bed lining, Lizard Skin, your choice. My car is epoxy'd and undercoated inside the doors.

I never use peel and stick stuff for insulation in the doors because moisture will get in between it and the surface of the door and cause rust. Mine is usually daily driven so that would be a huge problem for me, but it could also be a problem for you if you're in the habit of washing your car...  I've also seen some people having issues with the peel n stick stuff falling off after lots of heat or moisture gets to it (though some products have better adhesives and don't do this).

I used ceramic rattle can bedliner coating.  I chose this over rubberized undercoating. There is just something about a pliable coating that makes me feel like moisture would get through it.  The bedliner coating dryies and stays hard which makes me believe the water will flow and not absorb.  Be sure to keep your water drain holes free and clear at bottom of the door.  Tape the hole from the outside when spraying to avoid overspray, then remove tape when done.

67StangMan wrote:

Sound deadning a vehicle is so misunderstood.  There's a lot to it, to do it correctly.  A rattle can helps, but does not compare to a properly installed sound deading system.
To do sound deadinging correctly you need three layers of material; sporradically placed CLD tiles to dampen vibration (doing the whole floor with stick-on is a waste of material and $$ but the manufactureres won't tell you this) + closed cell foam of about 1/8" thickness + toping of MLV.  Educate yourself here: http://www.sounddeadenershowdown.com/home
 

Exactly the correct info,,,  the correct sound freq / wave lengths that are trying to be suppressed is known as "Sone"  these freq are the most disturbing to humans,,   I used the above system to encapsolate my interior of a 2009 Honda Accord.  Starting dB over various surfaces 74-78 dB.   Now after new tires 69-72 dB.  The biggest gain (lost) was in the tires.  I took pictures of the install in varous steps.   This link gives the basic way to go.  NOTE Dynamat is a vibration dampener NOT a sound blocker.