[chrismorse]

With the trim and drywall removed you can tuck insulation, or if the void is extensive, hire a foam or cellulose blow in artiste to fill all the wall cavities, (after any electrikill or plumbing).

Next, foam around all window gaps.

You may want to consider placing sound board over the interior sheathing before the drywall. This would entail packing out the window and door jambs - no big deal.

Good luck.
chris