Suggestions on sound deadening new quarter skin?

I'm in the process of installing new quarter skins on my Charger. I was going to spray a few heavy coats of undercoating on the inside of the skin first to help get that "tinny" sound out of them (keeping it a few inches away from the edges so I don't get a fire when welding). The original stuff is nice and thick - body schultz I think they might call it?) Anyone have any better suggestions? I read about something called "Lizard Skin", but it looks like an over $200 investment with the special gun and I'd like to avoid that if possible.

If you're going for true damping then you can glue on the dense pads from Eastwood in a few places. You might want to tack weld some metal tabs to help hold them in place as I don't know how good the glue is or if it will fall off due to heat (i.e black car). Otherwise I'd just spray it down with a few coats of the mud.

http://www.tcpglobal.com/detailsupplydepot/itemdetail.aspx?itemno=UPO+0821V-GUN
Never used this stuff, but i have heard some good things about it. I am going to use the tintable kind under the bottom of my dart. You can get it in a kit with a gun for like $125.00. Going to try to post a link as well. I would do this or anything after i get finished welding the quarters in. You could get the tintable type and let that be your finsh coat on the insides of your quarters.
Matt

The bedliner material might be worth considering. I've seen some in quart size at Checker Auto Parts.
I have an 98 Ram with spray in bedliner thats been in Arizona heat all its life. It has dried some but is still stuck like glue.

Some good suggestions guys, thanks. I was drawing a blank trying to think of anything other than undercoating so those are three good ideas.