I've always used Peel N Seal from Lowes or Home Depot. Way cheaper than Dynomat and in my opinion does almost as good as job. The only down side to this product is if you are in warm states in the summer it doesn't hold very well to doors or roofs. I only use it on my floors and never had an issue.
Here's a picture from it installed in my 64 impala
You won't convince anyone to use it, I've tried and everybody HAS to use the overpriced, extremely difficult to remove and piss off future restorers, fat and dynamat.
The Home depot frost king duct wrap is way cheaper, easy to remove and has been on the roof and floors of my Charger since 2010 and is stuck as well as the day I put it on...
Later