Good to know about the free blower. However, I think for ease of future changes, I may go with rolls of insulation.
I REALLY considered just drywalling a second layer over the existing drywall -- but:
1> It's in pretty bad shape (holes, stains, lots of nails).
2> The electrical looks like it was put together by a committee -- with some outlet boxes stuck at random places flush with the drywall, or out in the room, or in the ceiling.
3> I'm worried about the condition of the inside of the exterior wall behind the existing drywall -- and taking out the old drywall would let me check it all out, clean it, and seal it with some primer.
But maybe I'm being overly cautious! Perhaps pulling off just the worst one or two sections of drywall, and seeing how it looks underneath, would tell me whether to proceed by removing it all, or fixing what's there.
Note that I only got ONE BOX of green glue, so I need to concentrate on using it in the most impactful manner. From what I can see, this means using it where the studs meet the drywall, which would take less glue than using it on a second later of dryall.
But I could be completely missing the boat, and would appreciate more insight / experience to help guide me!