As kaashifv said, Megs has a good set- another thing to consider is the
Meg's leather conditioner gel- it's clear, so it won't plug the perforated holes with white residue after the product is absorbed.
Another thing you can try is a wet magic eraser, with light circular pressure. They are abrasive, but I've been using them for years with customer ok, to detail dirty leather and interior panels.
My 2000 Explorer seats:
Before on the right 1/2, after on the left half, immediately after cleaning:
What came off:
After they dry (stitching will whiten up), apply 2-3 layers of conditioner, and they feel amazing. Keep them conditioned weekly...