I shave front to back, or more exactly top down. When I used to use mach3s I went both ways. Nowadays I only do the one pass, but I shave my head almost daily to compensate. James.
I shave front to back, then back to front. After that I do touch ups. I use a Merkur 1904 or a Classic long. I tried using my Star 1912 and it didn't go so well.