foil backed asphaltic based flashing used for sealing windows and doors is NOT near as effective as a butyl rubber based product specifically designed as a constrained layer damper (CLD) tile to lower the resonance of sheet metal when properly applied to the correct places. Also importantly, if you happen to live in a hot climate and/or park your truck in the sun where internal door temps can reach elevated levels, the asphaltic based products will fail and slide down inside your door leaving you with a gooey mess to eventually clean up while doing absolutely nothing to control panel resonance since out is no longer attached to the panel where you thought you had stuck it.
That being said, there are, in fact, significant differences in effectiveness even between CLD products sold for car audio use. DynaMat, the most commonly used brand, is one of the least effective, but the KnuKoncpetz Kolossus brand (hokey as the name may be and sold though Amazon) is one of the most effective in lowering panel resonance. This conclusion, is as noted by a TLTR research thread on diyma.com
Also importantly, do know you do NOT need to use a CLD at 100% coverage, but rather stick some in the center of flat panels at up to 30% coverage for it to be most effective. While you CAN use more CLD tiles, its rate of effectiveness at lowering the panel resonance and vibrations becomes less cost effective at over 30%, so it becomes a waste of your hard earned dollars.
That being said, and MUCH more importantly, while you are doing the CLD application, using an additional layer of CCF (closed cell foam) and then MLV (mass loaded vinyl) will SUBSTANTIALLY quiet down the interior of truck and make it a MUCH better listening environment, instead of only making your doors a lot heavier!! (LOL)
If you want to read more on how to do it RIGHT, check out the "how-to" section of the website sounddeadenershowdown.com.
NOTE-- I have nothing to do with the business, and you do NOT have to buy his products, which ARE fairly expensive, but know that if you DO buy from Don at SDS, you will be buying the best made products for the job and they are backed by solid performance, great packaging and top shelf customer service as well.