Homasote!  I haven't heard that in years.  When I was a kid, my dad built a tool shed and a dog house and sheathed them both with Homasote.  Both structures held up to Pennsylvania winters for about 5 years.

I like the resistance soldiering rig--I may have to try that.  I have an old Weller soldering iron, but I find it too imprecise for this kind of work.