Depending on whether they use it in your part of the country, you can get peel & seal from a roofing supplier as well.
I hear that Rust Bullet is better, but my experience with POR-15 (which I had access to) was to just brush off the rust, and paint it on. Do not use on clean metal or it will peel right off. On a clean piece of metal, I left it outside over night after hitting it with the water hose, then brushed off the light rust coating, and painted it. PERFECT! I did it over all my floors, inside my doors and fenders (which already had a coat of thin rust), much of the undercarriage. It does NOT hold up in direct sunlight. I have an experiment going on my truck from 3 years ago where I put it on a rusty spot. The spot hasn't grown, but the POR-15 is fading and getting crispy. I still have not messed with it, so touch base with me in another 3 years to see what it looks like then...
hey rthomas771, when you say bed liner, are you talking about something like rhinoliner like i have in the bed of my truck or something else? where exactly would you put the peal n seal to deaden the sound? all over the floor under the carpet? inside the doors? and all over the inside of the trunk? basically coat the whole inside of the car? sounds like a lotof peal n seal and work but if it makes it sound like the lincolns from the good old days, then im in.
I used this stuff http://store.summitracing.com/partdetail.asp?autofilter=1&part=SHW%2DTRG250&N=700+115&autoview=sku and mopped 2 coats on with a paint brush. The type in a spray can is too thin. I still need to coat the inside of the door skin and back side of the door webbing staying away from moving parts. I though I might as well wait until I remove the door panels when I dye them instead of taking the door panels off and on several time. I'm thinking of not coating the very bottom of the doors to help them drain water. I also used this bed liner on the front inner fenders. I haven't applied Peal & Seal yet. The weather turned to cool when the time came. I will tackle this when it hits the 90 degree weather. I plan on doing the toe board, floor and on the wheel house behind the rear quarter panel trim. They say most of the road sound will be coming from the wheel area.