How do you dry insulation inside a wall/ceiling cavity or the backside of the wallboard?
The BEST solution with wet insulation is to replace it. Wallboard can be dried in place if there is no obvious swelling, the seams are intact, and you can get adequate airflow to the wet surfaces. If not, remove and discard the insulation. Wall cavities should then be ventilated and dried.
I’d be lying if I said I never violated this principle. Several years back, I had two simultaneous ice dam leaks in my house — prior to installing a new roof with an ice and water shield. Luckily, I was able to stop the leaks within an hour of noticing them.
I did not open up the wall because I have extensive wainscoting and crown molding. That does not mean mold did not grow in that wall cavity. I’m sure it did.