THANKS to everyone who responded to my query. Wow, what a network.
Only thing I can think of to do is either call an upholstery shop and ask them, or springle baking soda all over the couch, let it set for at least 8 hours and then brush off, that will take care of the smell only. Try vinegar for the mold but test it for colorfastness
The best way to remove odors, mildew etc is professionally. I found a place that specializes in restoring smoke damaged furniture for businesses etc. My sofa was musty and heavy with doggy odor
from my ole dog sleeping on it. For 50 dollars, they
put it in their ozone room for a few days. It came out smelling like new...they even cleaned a couple of spots that I couldn't get out. I did have to deliver it, but boy it was worth it and no messy work on my part.
Newspapers, charcoal and baking soda are great for absorbing odors. If you have access to the underside of your sofa, try stuffing crumpled newpapers in and around the springs. I'd sprinkle the upholstry with baking soda, brush in, leave it there overnight then vacuume, repeating the process several times if necessary. Also, placing the piece outside in the sun should help if that's possible. Fabreeze is a good freshener, but I don't know if it would do a lasting job.
I don't think that the slipcover will shrink if you wash it in cold water on gentle cycle using a mild detergent like Ivory. The mildew smell, gee, I would try spraying it down with upholstry cleaner and after that dried, spray it down with a gentle mist of Lysol.
There are also "fabric freshners" on the market that would probably help. You can get the inexpensive kinds that work well at a dollar-type store.
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