I would never clean a spinner mirror with dry cloth. Depending on spinner type and speed rating the polished surface may be easy to scratch. I say it's safe to use IPA. Use special dry cleaning tissue for optics or microfiber cloth for household window cleaning (yes it works fine don't laugh) , soak with IPA, swipe gently don't rub. I always use latex surgical gloves to avoid finger grease contamination on spinner mirrors and lenses. Do NOT rotate the spinner rotor by hand.