Lightly damp towel only if really really needed.
Else, use vacuum cleaner with "just enough" power, don't go for high (use an adjustable one) and do that (1 minute) after each session or daily.
That way dust cannot settle into the cloth and everywhere else.
Balls cleaner is nice, but a lot of work or money.
Again usually use microfibre cloth and use more time on the white.
If really dirty can be sprayed with Isopropanol or dishwashing detergent, rinsed and rubbed dry again carefully, too.
Use Magic chalk, yes. :grin: