I have been shaving my head for past 10 years. Started when i was 19. I use a gillette mach 4 and whatever shaving cream i can find. First couple times of shaving it make sure you use a good aftershave or even isopropyl alcohol. If not your head will look like hell. I can shave my head in about 3-5 minutes now. I shave about every three days. Usually get about 5-8 shaves out of a razor before I have to change the blades.
If you have anymore specific questions send me a pm. I have tried just about everything to make it easier or faster to shave my head.