Jon Cone (inkjetmall.com) has a number of products for cleaning printers. Check out his video for the 4900 on YouTube at http://www.moneychimp.com/features/market_cagr.htm.
I can't personally speak as to how good these products are, but I'm willing to believe that they are much better than the generic Windex and ammonia solutions offered from less reputable suppliers.
Homer Shannon