I like the car detailing spray idea. Also a swiffer duster is really good to have. What an incredible invention this was and how stupidly simple it is.
No one mentions use of distilled water, which is a lot better to use versus tap water.
Amazing answers herein.
A Clean microfiber cloth is probably a good idea. Glossy finishes on speakers can be pretty damn incredible.
I think polishing glossy surfaces is probably not a good idea. Cars you need it because it protects against all the Dust and air flow.