The flexible solar panels on my boat have oxidized and have a hazy appearance so probably not very efficient. What's the best way to clean or polish them?
Not sure if modern panels are the same but older ones had plastic film laminated on top and this eventually went opaque and peeled off in some cases so little could be done to clean them up. I would try LadyInBed's idea.
Only very light pressure. Many polishing attempts have resulted in invisible micro-fractures within the cells that ruin them within days to weeks, and they never knew why. This is well known in the industry.
The best answer is to wax them (will help some) and then leave them alone. The fog is through the plastic and you can't really buff it out anyway. The haze does not cost as much power as you may think, and far less than a few fractures.