Spray 9 worked great on ours.
Marine Strip - used on Fenders and powercords. No scrubbing, just wipe on and wipe off.
black paint
My regular used fenders are already black. Much easier to maintain.
I have 2–21” round white fenders, they’re 10 years old. I use when locking or when tied to a sea wall and they’re scuffed and scratched and work as good as they did 10 years ago. I clean with a pressure washer. They will never look new again to many locks.
Always looking for a better cleaner.....
Seems like Spray Nine is less that half the price of Marine Strip, which is quite expensive.
So the question is Marine Strip worth double the cost?
I have covers but remove them for dirty locks and replace them after traversing a canal and rinsing the fenders. The covers stay cleaner and are softer on the painted hull.Can't help with the cleaning but if you can't get them back to original then maybe buy some fender covers.