They'll be issued a toiletries box that has a Mach III razor in it. I've never used one, but from what I recall, the electric razors didn't do a good enough job to avoid detection. In the first few days everyone tried to use shaving cream and do a good job, but after taking way too long, we went to just using water and found it to be much faster and could get closer than an electric.
I haven't used shaving cream since...if I miss a day, it's painful though. It'll take 2-3 days to figure out what works, and from there it'll be just another routine.