Those various angles/spots you cannot quite get now will easily come with experience and those ah-hah moments. Directly under my chin requires a contorted left-hand, scything stroke going directly from the right to left sides of my neck. Took me quit a while to get that area as smooth as the rest of my face.
Another issue I started off with was the bottom of my neck where irritation resulted from neglecting to shallow the blade angle enough.
Welcome newest member to the burgeoning Canadian contingent here at SRP. :)