For crosswind landings, get them to side-slip from 500 all the way, then 400, then 300 etc til they can transition in the flare
Horses for courses but I would be concerned that style of instructing raises more questions than answers.
Sideslipping any aircraft causes erroneous airspeed readings which is the last thing a student needs near the ground. Secondly, there is the possibility of loss of elevator effectiveness in steep sideslips due to extended flaps blanketing the tail surfaces. This can occur in high wing types and even the Cessna 172 POH discusses this. Thirdly a continuous side slip means unwarranted side stress on the fin and rudder.
Better to demonstrate the standard crosswind procedure used for time immemorial of tracking the centre line normally by maintaining a heading to allow for the drift angle. Don’t always use extra airspeed simply because there is a crosswind particularly if the runway length is marginal. At the flare use sufficient rudder to align the aircraft with the centreline combined with sufficient aileron to level the wings during the flare or touch down slightly one wing low into the wind to touch on one wheel.
All this should be carefully explained during the preflight briefing. Even then, some students will nod politely as you prattle on even though they have lost the plot half way through the briefing but won't admit it. In that case get the student to repeat the technique back to the instructor. Only then will the instructor know if the student has thoroughly understood the why and when’s of the technique.
Even some airline pilots have trouble with crosswind landing techniques because they never fully understood from their ab-initio training years ago, the correct method. Believe me, there are pilots out there who have gone through their whole career secretly dreading crosswind landings.
