If you have soft ducts (fiber glass, not sheet metal) for AC those could absorb the smell and have it return every time the AC kicks on. 

Their weight deformed the fiberglass shower pan just enough to cause a leak at the drain.

I am debating between spray foam and regular fiberglass.

The fiberglass screening he's talking about is just regular fiberglass screening.

Do you have pieces of fiberglass batts stuffed into the rim joist bays?

, well maintained and well located house or class B/C building in a real neighborhood with decent sized units you are probably all full.I had a vacancy (1brs,  Burien downtown - adjacent municipality 15 minutes to downtown seattle)  in April around the peak of the first 'wave' of COVID and it filled in about a week with the highest credit score applicant I have had to date -  rent about 25% higher than prior resident,  with some light renovations,  mainly vinyl plank floors and refinish the pink fiberglass tub.

Fiberglass or resin of some sort? 

Hey Dave,I just caught your asbestos example, funny you should mention this as I am under contract for a beautiful 2 fam built in 1932 with a steam heating system and you guessed it the steam mains in the basement are covered in asbestos insulation.The seller actually the executor (ths is an estate sale) has agreeed to remediate and reinsulate with fiberglass which is what I asked for.'

If the ceiling is uninsulated I would buy batts of fiberglass insulation and roll them over the ceiling (if you plan on remodeling do not attach them, merely roll them up, store them during remodeling and then install properly).

The fiberglass is a bit stained and off-color in some areas; haven't yet tackled the detailing of this.