rain-x still makes a spray but it has a warning CAUSES EYE IRRITATION. most anti fog remedies are wax. you could wax your visorA trick that used to help me when fogging started to show up was pulling my lower lip (and teeth) in a pit and bringing my upper lip out and down a bit, so that exhaling through my mouth would go down, rather than forward toward the shield, then inhaling through my nose and exhaling through my mouth. Might not help in your son's case, but worth a try.
I didn't know Rain-x made anti-fog wipes, but back when I still needed to wear a helmet, they sold anti-fog fluid in the same type of small squirt bottle that regular Rain-x came in, and it worked very well. Might look and see if they still market that.
I used rainx.it worked ok but only for 1 night. Also if you touch visor it fogs where you touched it. I don't have any help on race day so remembering to do the video routine does not happen basically ever. I'm looking for something that is just done and over with.rain-x still makes a spray but it has a warning CAUSES EYE IRRITATION. most anti fog remedies are wax. you could wax your visor