If you're not too worried about your car you can always use peel n seal or other related products more focuses on mass loading, but if it doesn't work out for whatever reason or another don't be surprised when you're trying to get it out. If it does work for your application; great you saved some cash.
I personally like SDS tiles, but I don't go for 100% coverage. After that I would lean towards second skin or knukonceptz unless you happened to find middle of the pack deadener on sale or for a decent price.
- For mlv and acoustic barrier I like Home Depot's generic stuff as per Keep_Hope_Alive's build log. It works fine and shipping is reasonable.