I would never use a pressure washer on my deck - not even a strong spray from a hose sprayer. I use a chamois headed mop and then for tough spots a very soft brush. And I always wipe across the grain to avoid eroding the softer
wood that runs between the grain.
I have used Joy but for the last several years I've been using the cleaner from Teak Decking Systems in
Florida. These guys build teak decks for superyachts and
cruise ships. The cleaner does just what you are looking for - it makes the teak whiter not browner by pulling all of the black mildew and dirt out of the grain. Their description says:
Teak Cleaner Liquid is designed to be gentle to your teak, caulking, hardware or paint. Teak Cleaner Liquid is water-based, contains no acids and is designed not to harm the environment.
I don't wear gloves. It also doesn't seem to hurt stainless,
aluminum or plexi.
They have a powder and a liquid. The powder is designed to be used weekly! (I guess that's an advantage of having a
cruise ship crew). The liquid is supposed to be used monthly but I get by with twice a year. I also keep some premixed in a little spray bottle for the occasional spot. I buy mine at Jamestown Distributors.
Carl