The first time I shaved my head bald, I used an awful old electric and it left red scratches all over my scalp. It looked like I lost a fight with a bobcat. Then I started shaving against the grain with a Gillette Fusion and Headslick. After a few months of honing my technique, I was able to get perfect shaves with no bumps or irritation. I would recommend using a good razor (fusion, mach 3, etc) with headslick or bump patrol shave ge land go with the grain until your scalp gets used to shaving.