scalp massaging with a shiatsu machine

I have an older style shiatsu foot massager. I don't think they make them anymore but it has two rotating plastic balls that you put your foot between. It only massages the sides of your feet basically. I am now using it to massage my scalp. It seems to grab the skin on the sides of my head and pulls up and down in a circular motion. You can change the direction of the rotation but one direction feels better than the other. It does feel a litlle tight sometimes and the motor is pretty strong so I may have to modify the balls by filing them down a bit or replacing them with smaller ones. But it does do a good job at tugging and rotating the scalp. My scalp is pretty red after using it for a few minutes.