Pádraig gets his voice going by starting with a big yawn. Wikipedia says that “a yawn is a reflex consisting of the simultaneous inhalation of air and the stretching of the eardrums, followed by an exhalation of breath. Yawning (oscitation) most often occurs in adults immediately before and after sleep, during tedious activities and as a result of its contagious quality.”
Exhalation of breath is what you need to blow bubbles and to make a sound. Makes all perfect sense. The rest is ‘just’ practice.