How do we teach and learn technique

A question I cannot seem to get away from is: how do we work on technique? Do we build a dispassionate skill, and then apply it expressively? This seems to be the method of those who drills hours and hours of Czerny. Or should we, as my pre-college teacher Lois Nielson preferred, learn our technique from the repertoire? This seems to produce a technique that is hopefully connected to expression, but may be more uneven in terms of areas studied.