Step 2: Wash The Parts
The robot is old, and therefore dirty. He'll have dirt in places that you won't get to with a cloth.
So throw him in the dishwasher! AKA the robot spa, as I call it...
When he returns from the Robot Spa, use a wet rag to wipe off any dirt that was not removed by the dishwasher. The dirt will be very loose and easy to remove after the dishwasher.