I read sometime back that best way to keep your electronic screens clean was a mixture of distilled vinegar and water at 50/50 followed up with a microfiber towel.
I keep a small spray bottle and microfiber cloth in a ziplock bag in the boat. Takes two seconds and works like a charm at quickly and easily removing water spots, stains etc... I often will use it a couple times during a trip.
Just thought i would re pass it on as it is such a good tip!
Robert