J.S.
My advice would be to not put the pull up back on him. Take him off the potty and let him run naked. He knows when he has to go. He will run back to the potty and let you know. Running naked has been how both of my boys have trained it has been very successful. I don't do Pull Ups they are just like diapers to the kids. It allows them an easy out.
Celebrate big time when he is successful.
We also did lots of potty videos. mine loved and still do...Elmo potty time.