i'd offer a potty time immediately upon awakening in the morning, before and especially after naptime, before bed, and any time you've noticed he regularly goes. I would maybe sit together- you on the real potty, him on the little potty? Those are generally good times to make a catch. No pressure at first, just trying to get him used to the potty and what it is for.
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Then some nakey time. With my DS, we would have an hour or so in the morning, and worked up to 3 hours or so, then started all day. We'd have a little potty in the room where we were all the time and he'd basically wear a long t-shirt and naked bum. He was good about taking himself pretty quickly, if he was naked. In undies or a diaper, he'd just eliminate there.
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Also just start talking more about it. Does he know when he is wet or dirty? Can he participate in diapering? (have him put the diaper into the pail, have him flush the toilet after the poop is in there). This also gets him aware of his elimination and the idea that eventually he will take care of it all himself...