Range should be taught as a planning exercise. The POH should be used to calculate range. Emphasize the use of mixture as part of range.
Endurance can be calculated using the POH but endurance is not usually planned in advance. The practical method should be taught as it also considers the current weather, density altitude aircraft weight, and aircraft condition.
Give practical examples of when endurance should be used: such as snow removal, fog, disabled and aircraft on the runway. Holding outside the zone waiting for clearance in for landing is not a good example. There may also be others doing the thing and aircraft milling around in the same airspace with no high attitude, poor lookout visibility and sluggish control response is a recipe for disaster.
My fam demo for slow flight at the end of the endurance exercise is to have the student put the aircraft into endurance one more time. I them take control and show them that if the pitch aircraft attitude is increased slightly we will be in slow flight and power must be added to maintain altitude.