Having potty trained two children, I know that this part is especially difficult. Actually using the toilet is fairly straightforward. But the manual dexterity to wipe effectively after defecating is tricky, especially when the child can't see what he or she is trying to do.
Redditor /u/Sakgeres introduces us to this clever technique used by an unknown preschool teacher. The balloons are an adequate simulation for buttocks and might help the child visualize what the hand behind the back is trying to accomplish.
But, as some commenters point out, it would be best to teach kids to use a wad of toilet paper only once.