Anyone who is restoring a tractor will undoubtedly have cloudy lens's. Since these are not road going
vehicles, damage is usually limited to oxidation and minor scratches. If your lens's are only slightly cloudy or foggy , a deoxidizer such will likely clear up your troubles. Any one step lens restorer will be some type
of deoxidizer/polish( Meguiars,Mothers, Blue magic,Turtle wax and many more im sure).These lens's were done with Meguiars .
The tail light lens shown has some minor pitting and scratches that the camera flash and lens really show up . To the naked eye these lenses look perfectly acceptable.
If your lens's have deep oxidation, scratches or pitting you will have to Wet sand and polish.
just as if it was you prize paint job.There are many HEAVY DUTY lens restoration kits out there,
but some wet sandpaper of different grades such as 1000,1500, 2000, 2500 etc.Then some plastic polish.Mother's,3M,Permatex, etc.Will do the job.The more time spent the better the result's.
Most important part is protection. I have been using regular car wax on my plastic lens's on all my vehicles for decade's, and even after 21 years in one case ,the tail light lens's looked excellent. Until i retired the truck from bush/hunt camp duty 2 years ago (sorry no pics).
KEN