I have a Logitech cordless trackball which I find easy and comfortable to use. However, the ball tends to get sticky from time to time. There are four screws in the base and I would like to know if it is safe to take them out to get at the inside for a bit of light housekeeping. I haven't dared to do this so far because usually when I unscrew something a vital part falls out and rolls under my desk. And what is the best substance to use for cleaning?