Preferred method for removing mold & mildew from album covers

I've replaced quite a few covers surfing in good will or similar stores. For smell you can use Ozzium. The way it works that you should place your smelly items let's say inside your car or bathroom sprayed all over with Ozzium and than close the doors for 20...30min. The car would work best
With goo-b-gone I cleaned large number of album covers as part of my business. Nothing work best there.

Check out eBay - your source for album covers in great shape and LPs inside in crappy shape.  Good luck.

The other alternative is to not worry about the covers for now, and buy some high grade plain cardboard jackets- I like the white ones with the cut out in the middle sold by sleeve city. I use these in connection with new inner sleeves for repacking some records after cleaning. If you want you can write on the jacket in indelible marker or use a sticker (i do the latter) to better identify what’s in it. They offer pretty good protection as well. Mine are usually then bagged as part of a larger package for each record, but you don’t have to be obsessive about it.