Ya can't 'teach' Airmanship really it's acquired as experience is gained.
While I agree that airmanship is a subject that is (or should be!) continually learnt as one gains experience, I reckon there is scope for teaching it.
During the pre-flight briefing of every sortie taught in ADF flying schools, airmanship is discussed, i.e. airmanship points pertinant to that sortie. The idea is to get the student thinking about airmanship every time he/she goes flying.
So can airmanship be "taught"? Yes, but to a limited extent. It is the duty of the instructor to get the student on the right path to learning about airmanship. The rest is up to them.