For the last (at least) 20 years I have used (and will continue to use) Mother mag polish.
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www.mothers.com/02_produ ··· 101.htmlNowhere will they say that it's good for this type of use...but who am I to care ?
It costs less than any of the lense polishing kits, is much easier to find (hell, Home Depot and Walmart has it...and probably your local grocery store too) and there is much more than just a use or two in the jar.
I would never take any sandpaper to a lense since it removes the coating, and they are all coated.
Try it, 2 minutes tops per lense.