Really no need to clean the elements. Usually when the scale get thick eneough it will flake off. Scale acts as an insulator on the element. As the layer gets thicker the centerline temperature on the element rises in order to drive the heat flux through the scale. If the scale gets thick enough and does not flake off the temperature will reach a failure point and the element will burn in two.
To reduce this temperature, I have had my WH wired at 120 vs 240 volts for years. Of course it heats at only 25% (1125 watts).
Soaking in vinegar to dissolve the scale might be easier on the element than mechanical removal.