DO NOT USE PEEL AND SEAL!!!!!!! to put it bluntly ... a half ass product yields a half ass result ... If you are looking for an affordable option go with Audio Technix Deadener
It is a great true Butyl deadener, I have over 5 rolls all through out my car You will notice a difference after 2 layers and it wont melt off like Asphalt based deadeners do .. you will want to focus on doing your floorboards and rear fender Tubs more than any other areas ... Though a layer or 2 over other areas wont hurt ... If you pull the foam from your foot wells you will eliminate alot of engine noise also.
In my personal vehicle I have 6 layers on my roof 3 layers on my floor and 4 on each door . It is solid