>>Have any of you found a good solvent for removing that junk?

Jake:
I removed all of the fiberglass insulation from the walls of my vanagon Multivan and replaced it with FatMat, a butyl rubber sound insulation sheet good with adhesive backing.  Like others on the list, I used a less expensive foil/bubblewrap material in some areas of the van as well.
The FatMat was about a buck a foot and ended up being easier to install once I got used to getting it stuck to the van and not everything else it came close to.
I used GooBGone to clean off the residual adhesive that VW had used to adhere the old insulation.  I only had to clean that out of the panel behind the folding table (driver side) and the sliding door.  In both front doors I had to clean the wax stuff they coated the inner doors with so that the sheet goods would adhere.  Did that with the same goobgone stuff.
Although I'm gonna sound like a door to door salesman here, I really do like the goo cleaner.  Use it to clean up a lot of my messes.  Would bathe in it if the smell didn't overpower my cheap after-shave!
Have some pics available on my site if you care to see my insulation process.
www.weidefamily.net/vanagon
go to Interior / Insulation

Thanks,
Brent

Brent Weide
Portland, Oregon
http://www.weidefamily.net/vanagon/