See here for finish care guidelines from the Piano Technicians Guild (PTG).
Most pianos that are sold have cases finished either partially or completely in black polyester high-gloss finish. This is very similar to the finish that you find on cars. Although the finish is very durable and relatively easy to keep clean it is still susceptible to being scratched, it takes fingerprints (but not as bad as a black polyester satin finish), and does tend to attract some household dust.
There have been threads on Pianoworld from time to time, asking what cleaners can be used to make a black poly finish easier to keep clean. There are a couple of made-for-piano cleaners and polishes that you can buy, but I’ve not seen any of them in Singapore (maybe because I didn’t look hard enough). What you must not use are the typical off-the-shelf furniture polishes, especially those containing silicone.
It is a paste wax, and easy to apply — just wipe on sparingly, allow to haze, then wipe off and buff lightly. Liquid waxes are too easy to drip and spill. The tiny bit of flaky residue (if you apply too much wax) is easy to clean up with Kao Magiclean floor wipes. Residue in crevices can be easily removed with a soft toothbrush and vacuum cleaner or a vacuum cleaner with brush attachment. The wax layer is just a few molecules thick, barely 0.000025mm. But the result is a lustrous and deep, ‘wet look’ gloss that only gets better looking with each layer that you apply.
Once the wax has cured it forms a very hard protective layer (harder than concrete) over the black poly finish. It is very difficult to scratch, doesn’t take smudges easily so fingerprints don’t show, it doesn’t attract dust, and is super easy to clean. It is also easy to remove with the appropriate solvents (which don’t damage the underlying black poly finish).
Carnauba wax can be used on glossy lacquered or varnished wood veneer finishes, but must not be used on satin finishes.
Unfortunately, One Grand products are not available in Singapore. I get my brother in the U.S. to send them to me. A can of Blitz Wax lasts forever if you make sure that it is always tightly capped so that the solvents don’t evaporate. You can get carnauba paste waxes in Singapore from brands like Meguiar’s and Zymol, but make sure that they are the WOWO kind (wipe on, wipe off). Avoid waxes that blend carnauba with other additives.