Well, Steve, if you did not have ADHD, or a physical problem, I could see why that might have worked with you. Not sure it would be a good solution is this case. And its pretty easy for a 6 year old to get a diaper off.
I would wait until he is calm, (not wound up and playing or rammy) and take him to his bedroom and pull his bottoms down and take out a diaper you already stuffed behind your back under your belt and put on the diaper. If he objects real severely, THAT's what you are hoping for. Then you say,,"Ok, you don't want a diaper on huh? Then are you going to do your Peeing and Pooping in the toilet from now on?? If not, then you are going to wear this diaper." My mom did that with me and it worked. I remember the incident.
Well, if he has something like ADHD, then he lacks impulse control. He will get busy doing something and not realize its time to go until its too late.
He could have a bladder infection that would cause the peeing.
He might have some sort of bowel problem.
He might have anxiety problems that could be causing this.
big question is how long has this been going on? Is it something recent?
What are the poops like - very hard, normal, runny?
Does he do this at school or only at home?