What's Best Care for Piano Black Finish Speakers?

My wife has a high gloss finish Yamaha piano, and has followed these instructions for many years with great success:

"The best approach is the least aggressive approach."

High Polish Polyester Finishes:
• Everyday maintenance - lightly dampen cloth with water, carefully wipe piano and follow with dry cloth.

• Greasy Fingers & Dirt - lightly dampen cloth with dish water solution, carefully wipe piano and follow with dry cloth.

•Occasionally - use Yamaha’s Extra High Gloss Polish, do not spray near strings.

When cleaning, she first uses a feather duster to remove surface dust (since the dry dust is abrasive). A soft, clean cotton cloth is her cloth of choice, and she always uses straight strokes, not circular motions. For the "dish water solution" she uses a very light solution of of Ivory Liquid dishwashing liquid detergent and water. Applying the Yamaha Extra High Gloss Polish is something she does only once per year or so (this polish leaves very little to no residue).

The cloth to which Mike refers is generically called "microfiber" - very soft, highly absorbant, no lint residue. It's also widely used for cleaning optics. I used microfibre for my glasses, my camera lenses, and my turntable (which has a gloss black gel coating and an air bearing arm which gets a wipe down periodically). Be aware that there are innumerable sources for microfiber cloth today, made from a variety of synthetic fibers for various applications, and some are better than others.
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Thanks, Larry. I appreciate your comments.