Spray or brush on material for inside sheet metal?

I just purchased a very nice early 90's 4/dac Technics CDP (SLP-50S) which sounds very nice but I would like to add a damping substance to the inside of the very thin sheet metal cover. Is there something out there which will adhere to the metal (add weight/isolation) and possibly improve the sonics? I've never even thought of doing this to other cdp's, but this one has so much potential for improvement I'd thought I'd ask for your opinions. (BTW, changed the stock ac chord (20-24ga.)w/
a Radio Shack 18ga. ac chord ($2.99) and the difference was noticeable.) Thanks, Bill