Factory wheelwells are not painted, bolts apear to be a phosphate finish. Painting is okay, but may begin to chip easily. Simple green works the best, with a low likelyhood of finish damage. The front wheel fenderwhells are essentially chopped black fiberglass. They have a spatter painted finish on the engine compartment side, and a rough black glass finish on the wheel side. I use a light scouring pad with simple green to remove road tar. The front portion of the inner fenderwell is part of your front core support. It has a smooth black gel coat finish that can be waxed after cleaning. Rear fenderwells are plastic. I would suggest not using any petroleum products like WD-40 or Armour-all on any of these areas, Particularly the front fiberglass areas. If you must use a protectant, then only apply it to the rear plastic panels, which will not absorb the liquid. When necessary I use "303 Protectant" very sparingly and wipe off all excess. "303" provides a natural plastic finish when applied properly, and does not attract dirt.
The best way to clean the suspension components is to use an old tooth brush with Simple Green. Clean the tooth brush with fresh water often. Gloves are a must (nitrile is best), and an engine oil tub works best under your work area to capture the waste. I also use a separate water bottle to wash off the simple green from the components. Care should be taken not to contaminate the ball joint grease with the detergent.
Some may consider this a futile exercise, who knows it might be, but you will spot any potential problems long before those that don't.