I carried a tinted visor in my side case for a day - bad idea. It got a bunch of surface scratches from the vibration/corners etc... and I thought it was toast. I ran into the Meguiar's stuff on the shelf in my local West Marine - it said it would work on face shields and... It works great. I used the Cleaner - and the scratches were gone in one application. The polish made it sparkle like brand new. Optical clarity was great and I could not see where the scratches were when I tried. it was about ~$20 for both bottles or over $50 for a new face shield. I cleaned up all my helmets, googles, and even a cheap watch face... so I'm happy to recommend the stuff.
Nice tip. :smile: I threw out a perfectly good Shoei clear shield a few years ago after it sustained minor scratches and couldn't get out at the time.
If you're going to carry an extra shield in your side case, might I suggest next time putting it in your helmet bag. It's free (at least when I buy a helmet I get a free helmet bag) and you won't need to buy $20 worth of fix-it polishes that wear off and need re-application.