Sound Deadening

I was googling for some sound deadening materials and I found this:
http://www.b-quiet.com/brownbread.html

Is this a decent material or would dynamat be a better choice?

As far as applicable places in the car go, I can only think of the trunk and door panels. Anywhere else?

I'm a big fan of secondskin, their butyl based adhesive is much better than any asphault based mat that I've ever used (dynamat uses butyl too). They are more expensive than the asphault mats though

And where would I apply this to my car?

sound deadener is not made for getting rid of rattles if that is what you are trying to do.

And where would I apply this to my car?

anywhere you can find a bare metal panel....

doors, floor, trunk, roof, pillars, and firewall just to name a few, the most important of which being the front doors, floor (mainly under the rear seat, if you have a rear seat), and the trunk lid.

sound deadener is not made for getting rid of rattles if that is what you are trying to do.

What does sound deadening do? Help keep sound from escaping the vehicle? Such as those vehicles with their stock setup that you can hear blaring outside of it when all of its windows and doors are up and closed?

What stops rattling on the inside and outside?

What does sound deadening do? Help keep sound from escaping the vehicle? Such as those vehicles with their stock setup that you can hear blaring outside of it when all of its windows and doors are up and closed?

What stops rattling on the inside and outside?

It adds mass to the panel, which reduces the vibrations and resonance. It can reduce rattles, but it all depends on what's rattling.

Overall it will reduce road noise on the inside of the car, and make the system quieter on the outside of the car, best of both worlds really.

the additional mass (of the deadener) lowers the resonating frequency .... below an audible frequency

THe mass also absorbs more sound. remember that sound absorbtion depends entirely uopn mass when it comes to soilds. ie 20kg of cement will absorb just as much sound as 20kg of plastic.