dismantle the laptop and remove all the things from the topcase means keyboard . remove trackpad also. after removing all the parts from the topcase you will see only keyboard inside attached only nothing else. after that wash it with soap or any handwash. after washing properly clean it with towel and leave in the sunlight for 5-6 hours from morning to afternoon. i had done this so many times. you will think how this possible but you can try this . best of luck