New to sound deadener, need some help
 

I picked up about 18sq/ft of sound deadener, and I'm looking for the most effective placement in my doors. I'm thinking of lining the outer skin (the part my speaker fires into) as the other side has foam/vapor barrier.
The other is making the door an 'enclosure'. I think 1 layer would work to cover the holes. The foam/plastic would reinforce it. Do I still need the vapor barrier if I'm covering all the holes?

What is more important? With the left overs I could try to cover as much of the other as I can.

As for cleaning the door, I hear Windex works good.

Any other suggestions?
Thanks.