My family has quite a lot of slides taken in the 60s. They've not been well stored, and there's quite a bit of dust and mould on them.
I bought an Opticfilm 8200i that came with Silverfast software. I've been pretty pleased with the results, but you need a lot of patience. I'm not a photographer, I just wanted to have a decent picture at the end of it, one not covered in little black marks.
The scanner has an infrared mode that can pick out mould and dust, and then the software tries to work out what should be there instead and replaces it.
It has a go at fixing parts of the pictures that are dark. It does a couple of scans at different brightnesses and then merges them.
Did I mention that it takes forever? Well maybe only about 8 minutes or so per picture. If you have a lots of slides it just feels like forever.
If you are interested in seeing the results, pm me and I'll send you a link.