This is a sort of Frankenstein arrangement. The Bulk of the song is played melodic style, but the C section is played Scruggs style. This mirrors the way most flat-pickers and fiddlers play this tune. The A and B section is played with accurate melody, while the C section is used to showcase shuffle bows, or cross-picking. There's a lot of great variations in the lick switchers. Be sure to check that out for some fresh ideas.
Sometimes there's an extra section thrown in after what we have labeled as the B section here. You can usually hear that in Doc Watson's version. However it's not that common.