Recommended product to restore black trim and fender flares

Except that most metal flares would be best served with a fresh top coat over how they come before installation... so the OP would be back to square one; flares that need to be painted! :ROFLMAO:

I have bought three sets in recent years. They've all come powder coated. Which is much better than paint.
 
I have bought three sets in recent years. They've all come powder coated. Which is much better than paint.

You missed my point.
Yes, PC is different from paint, but most aftermarket manufacturers apply too thin of a coat of it, and it doesn't last... especially on edges, corners, seams, etc.
Hence, buying a set of metal flares that have shitty PC on them isn't really an improvement over the discolored factory flares.