I use. Spray bottle of water and spray a very fine mist on my piano black speakers (GE Triton Reference), and wipe with a clean microfiber cloth. I have been doing this for the 3 years I have had the speakers with absolutely no swirl marks.
32 oz spray bottle filled with water and 1 tablespoon / .5 oz murphys oil soap, then use a clean dish towel. doing this for years on an actual piano black piano as well as two gloss black subwoofers.
