I use cake soap (Van Der Hagen) from Walmart, when I shave. I had always been a gel or creme user, but in 2005, in the aftermath of Hurricane Katrina, I spent 30 days in the Gulf states as a medic with a search and rescue team. We camped out or slept in abandoned buildings nearly every night. Not wanting to carry an aerosol can in my pack through very hot weather, I switched to a small lidded plastic bowl with a cake of soap, a shave brush, and whatever razor was available. I've never gone back. I recycle my wife's razors. I still get a few shaves out them when she's done.
I'm retiring in Jan. 2015 from a job that has required me to be clean shaven for the past 28 years. I will most definitely not be shaving on my thru-hike, and it's got nothing to do with hiking the Trail.
Beard-on, brothers! Let them bask in our scruffiness!