You can use a lens cleaner kit , which either has a small brush or a hole in the surface of the cd,(the brush is on the underside of cd) ,the brush type cleaners have a slight risk of scratching the lens as a result of close contact with the lens nevertheless you should not be worried about using that (little percentage of occurance).A second moderately risky method would be to buy a can of compressed air with a nozzle and spray it into the middle(location of lens)/where ever it doesnt jam) of the cd slot , that way the air would move all that dust/dirt that prevents the lens from reading cd's,it is moderately risky by that you could jam the cd loader with the airguide from the can,best done when the car is off.