Although my children are grown, and didn't have pull-ups back then, I had to use the "training pants" and had them potty trained in no time. (1 boy and 1 girl) At least only after a few messes. Anyway, I am now raising two young grandsons, one is now almost five and had him trained before he turned four. I used "potty treats", individually wrapped gummy candy, kept him motivated, and he liked to earn a treat. The other child just recently turned three. He wears the pull-ups also. I have been trying to get him interested in the potty, but to no avial. I have decided, it will just eventually click in. He sees his big brother in the bathroom, so he does have a role model. But in the meantime, I will continue to ask him, throughout the day, if he needs to use the potty?
By the way, I love the book "It's Potty Time", you can pick it up at Toys R Us. There is one for boys, and one for girls. It even has a button you push that makes the flush sound of the toilet. It is so cute. I periodically read it to my youngest and hope that helps him to get the concept also.