Eventually, most clear plastics will get scratched and need to be cleaned
There are three ways to do this, depending on the damage. After looking at all the pictures, this will make more sense.
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Only use plastic polish until the part is perfect
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Start with 2000 grit wet sand paper, use plastic polish to finish
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Start with 1500 grit, continue with 2000 grit, and finish with plastic polish
This Gauge Cluster Has Pitting From Armor All
After 20 minutes with plastic polish - Smoothed pitting, but still visible
Wet the surface and evenly sand the entire surface to remove the imperfections
Looks worse - But the pitting is gone (1500 grit sandpaper)
After another 20 minutes with the plastic polish - just slight swirl marks remain
All Finished
This was done with 1500 grit waterproof sandpaper. For a clearer finished part, I could have used 2000 grit sandpaper before the plastic polish to smooth out the scratches made by the 1500 grit. For less drastic surface flaws, just use 2000 grit and finish with the plastic polish. With very minor scratching, the plastic polish alone should be able to fix it. For worse surface scarring, you can try using 1000 grit sand paper first before trying the 1500 grit.
Disclaimer: There is a good chance that you will damage the part worse. Please practice on a parts you don't care about first.