I haven't used the dynamat but it's on my list for interior panels, Jeep went a little cheap on the MK's.
I did do the spray undercoating on my Challenger but it was more for the road grime and rust protection, road noise doesn't mean much when you can't even hear the radio over the engine
. The spray stuff is pretty flexible almost like the panels. Just clean the surface well with paint thinner/mineral spirits and spray. You may want to put a dab of grease on the screws, pins and other fasteners that hold the panels on so that you can just wipe off the undercoating from them when it dries.