insulation question

[sinistir]

so hopefully I can get some feedback from you pros so I can get some sleep. lol So I have been doing a half arse resto, more like refreshing. I have stripped the interior down to bare floors and firewall to repair a couple of minor rust issues and coated in por15. Now my question is before I put it back together I would like to do some sound deadening at the firewall and was tempted to install a dynamat or similar product, however, what if I need to do some further improvements/repairs in the future? Is that stuff a pain in the arse to deal with later? Or would a lizard skin type product be better? Or just deal with it until I can rip apart down to nothing later? you advice will be greatly appreciated.