Not totally sure but I guess it would take a bit of practice. In situations like this, I have given DS the words to say and then held his hand as he did it. It seemed to give him confidence and he always repeated exactly what I said. Although it would have been better if he had gone by himself he just wasn't going to and I hope that with time he will. He does seem to be better now. Maybe you can role play with some teddies and get him to teach them what to say in that situation.