As Pinklather said, a clear line of sight is to me less important than feel. My hands a big and clumsy enough that my old neck and shoulders creaky enough that keeping an eye on the surface of my face near the blade is very difficult, but I can feel exactly where the blade is I have also come to judge pressure very well. With the right angle, almost no pressure is needed...just enough to feel your skin/blade interface and then hear the whiskers being chopped off. The angle of your hand will also give you a clue as to angle of the blade.

I wish I had learned this art when my face and joints were 20, not going on 70. I bet with tighter skin and more flexibility, it would be easier. But there's nothing to do about that, so on I go.