Use science-physics and math as an explanation. Find articles on the science/ mathematics behind a standard shift. That might be an answer -- your son might translate that into visually seeing what needs to be done.LOL. No good deed goes unpunished or appreciated. I've going to teach him on a standard transmission, that's a dying art apparently so I want him to know how to drive one. So I'm really looking forward to trying to explain to a kid who sometimes can't remember if he needs to put the clothes in the washer or dryer how a clutch, gas pedal, and brake interact together....
Learned on a stick- back in '60's. New regional HS; drivers ed car not yet equipped with dual controls. Actually learned by side eyeing the teacher as he would, out of habit, clutch, gas, brake when necessary.