The difficulty level of the material from the fourth step is higher than in step three. That is mainly the consequence of the increasing number of moves needed to solve the exercises. Most of the topics require solutions which are 2½ move deep: White plays, Black answers, White plays, Black answers and Whites scores. That is why a good command and application of the topics from the third step are absolutely necessary.
Tactics are dominated in a large degree by the preparatory move. The immediate attack does not work yet and a preparatory action is necessary. All existing preparations are dealt with: luring, eliminating the defence, chasing, aiming and clearing.
Gradually, the positional aspects are going to play more and more (a modest) part in the games of the fourth step students. The best way to introduce this kind of vague topics is to use the endgame. The lessons about material advantage and endgame strategy contain many strategic issues. Furthermore, the lesson about the weak pawns makes students aware to be ( a bit more ) careful while playing with their pawns. The same applies to the lesson about the opening.
Anyway, it remains best to deal with the positional factors while commenting the games of the students