I agree with threating him like a baby. He gets zero privacy and no big kid priviledges. No going to friend's houses ,"because who will wipe you if mommy isn't there?" Until he can wipe consistently for a specified amount of time.
You need to discuss WHY he oesnt wipe. Maybe flushable wet wipes would help for a while?
My 5 yr old was doing that it just took reminding her when she walked out of the restroom. We would say did you wipe your butt, did you wash your hands, did you flush. It finally stuck and I haven't had to throw out nasty undies.
Geesh thats rediculous dont treat him like that. Maybe its hard for him to reach back there maybe watch him when he goes i know thats kind of icky and gives him no privacy but explain his bottom will start hurting if he doesnt and it will start to smell and other ppl will notice now obviously do this in a nice calm voice not demeaning or anything just tell him the facts and maybe it will be easier to wipe from the front if he cant reach back or maybe he is in a hurry to get back to playing or whatever idk good luck tho
Whoa. Probably not gonna go that far! Lol
But the video game idea is a good one!
Then start treating him like a baby and wipe his butt for him. Along with this remind him of all of the things that a baby can not do, like play video games, watch certain tv shows, etc.