A good brushing and IF you played in more than just dust, then maybe a damp cloth. I use either a can of air. (pc duster,) or a air gun of a compressor to blow away the dirt and build up.
A remington silicone cloth will get the dirt off just fine and not damage the plastic. I would avoid soap and water due to the metal parts inside most plastic frames.
Just my take on the cleaning with dish soap, dish soap is designed to disolve oils, polymer is made from a petroleum product (oil). I don't wash my car with dish soap for the same reason, automotive paint is oil based.