Sound proofing car

[lsmalley]

I have noticed that the interior paneling of my car tends to vibrate and rattle while I an driving....particularly over a very bumpy road. The interior doors seem hollow. Anyone else notice that on their car? I was wondering if anyone has tried to remove their door panel and interior pillars to fill it with something to help muffle the sound by keeping a constant gentle pressure on the interior paneling. Also, my trunk door is bare metal. I tried spraying some sound deadening rubberized paint on the inside, but that didn't really work. Was thinking about getting some type of material to line the think as well. Not sure what to use in the inside paneling, was thinking fiberglas maybe. Or maybe something thicker like foam cushioning. I also would like to do the interior roof of my car, it just feels like whatever cloth is on the inside against bare metal. No insulation whatsoever. Looking for some feedback of anyone that has tried this or if anyone can bounce around some ideas. Thanks guys.