The ideas used here are the same or similar to those used in Rattle in Cash. This is mostly because the tunes were chosen for their similar melodic shapes, so that they would be good companions – note the removed notes in bar 13 to mirror the same rhythmic feature in Rattle the Cash.
A ‘fidget’ is a note added in between repeated notes, either a step above/below the repeated notes, or a third above/below (a ‘skip’). The scale is a connecting note added in between notes that are a skip (or a third) apart. I’ve written an example below to demonstrate how these might be applied to this tune, averaging one variation per two bar phrase, but try out these ideas in other places to find what works for you.