just go to your local eyeglass retailer(my wife's an optician) and get a couple of their lens cleaning cloths, you can wash them in the washer when you need to, and they need no solution whatsoever, works perfect on the nav screen, takes off all spots & smudges, and it stores easily in any compartment
3m makes a really nice hi-tech lens cloth that they sell in most camera stores. I keep one in my car anyway to clean off my eyeglasses and sunglasses. Works like a charm on the screen. Removes everything, even fingerprints.