This arrangement is based on the vocal melody of the tune. Most great breaks should be, The melody is the heart and identity of a tune, and you should always learn the basic version of a song before going to a more complex one. So if you haven't checked out the basic melody yet, please do that.
The bum-ditty rhythm pattern is added in through much of the tune to add a little bit of rhythmic drive. For more flair and authenticity, explore some of the licks to listen to and learn some tasteful variations. The name of the game with Bluegrass improv leans more towards a theme and variation approach. We always want to honor the original tune, and not just play all licks. There's a place for that - but eventually, and usually - we want to come back and not stray too far from the melody.