I used to struggle with this big time and sometimes now as well. This would work for me. Lie down - hand on tummy - inhale into tummy - exhale slowly and start an aah sound as you exhale. Slowly and deliberately. Start with just the aaah and oh sounds. Practice often. Practice when standing up and alone as well. Add a simple word to the aah sound once you have practiced just the aah Sound a few times. I think in the end we have to get used to speaking deliberately while exhaling only.