It does not take much strength to bring a light school cane to an effective speed. It is mainly a matter of technique and timing – coordinating wrist flick, arm swing, and torso unwind. A competitive squash or badminton player is likely to be able to cane very much harder than a near-geriatric headmaster.
The size, weight and flexibility of the cane has a big effect on the severity of the punishment. Soaking a cane in water “to make it more flexible” makes the cane significantly heavier and more dangerous and more painful. A beating with and iron bar, or something approximating to it, is always going to be more severe than a similar number of strokes from a feather or similar.