Explain finger drumming, is that just rolling your fingers over the desk top or other hard surface?
Like was stated in the description. Put your palms over your ears with your middle fingers around the back of your head near the base of your skull. Then put your index fingers on top of your middle fingers and ‘snap’ them down on your skull 40 to 50 times. Not sure if there is a correct way, I ‘snapped’ my index fingers simultaneously.
Good luck.