ice shield/peel and seal from home depot. it's dirt cheap compared to dynamat, and it's a thinner version of the same stuff. it's used for ice shielding when roofing a house. cheapest thing you'll find.
you can use expanding spray foam from wal-mart for areas you can't reach with matting, to reduce rattles.. but be careful with that stuf. test it and play with it to see how much it really expands before spraying it into hard to reach areas. too much and it'll start breaking things looking for room to expand beyond the volume of area it has
should come in a roll, aluminum on one side, adhesive on the other side. it's cheap, but it's thin so you may need more than one layer and the adhesives aren't as good for auto use as dynamat type materials.
the paint-on coatings work great.. if you gut the car and coat the entire interior sheet metal of the cabin, roof, doors, trunk, firewall, etc. I used a spray in liner for my own car but I had the whole interior stripped for paint at the time it was applied
so is there a spray that I can spray my interior metal to sound deaden it? whats some names and prices I was thinking of doing it I have lots of rattleing on the outside and it doesnt sound good to whoever I drive by
I myself used eDead.. ($50 a gallon for paint on), as well as truck bed liner. Not done yet, and my car does look pretty ghetto atm, with nothing in it but a car seat.. (decided to change my carpet color, dash color, etc, all at the same time while I was at it, heh.)
be careful with truck bed liner not to use any that are asphault based. those are the ones that smell.
lizardskin is good because it's lighter weight due to it's makeup, and it's designed as both an insulator and sound damper. it reduces engine heat and outside temperature transfer by up to 3 times if I recall. Anyway it is expensive, but it's the best stuff I've found for doing the entire inside of a car from trunk to firewall.
I wanted my undercarriage looking show quality so I sprayed the interior floorboards front to back, including the firewall.. and laid factory carpet over that. worked fine for me.
GlassWolf, how did it work? And big question..did you remove the paint first? On the truck bed liner, it says you have to remove the paint first for it to be effective, and I have noticed that it does peel off very easily in places with paint...