It may sound bad but I really limit drinks during the day. I was personally never a big liquid person so I just dont think about drinking things a lot. It probly wouldnt bother me if I didnt have something to drink all day.
Ive sort of passed that on to my kids. I give them one drink in the morning with breakfast, a small one at morning snack, one at lunch, a small one at afternoon snack, and no more than 8oz of milk at dinner. I also make my potty trained 4 year old pee everynight right before bed. Now he just goes to the potty out of habbit.
I dont know if it helps but I water everything down except OJ and milk. Water seems to pass through the body faster so maybe it will leave him before bed?
Also..
Does the pull ups have that cold senser on it where when they start peeing the pullup get cold?
I know when its cold outside I seem to be able to hold "it" a lot longer.
....another thing to consider....
The only times I have come close to bed wetting (even as an adult) is when I dream Im going to the bathroom.
Maybe its just really on his mind when he gets to wear big boy panties that "I AM going to go to the bathroom to pee if I have to". That being the last thing on his mind maybe he is dreaming about it and actually thinks hes at the toilet