It is hard to understand why somebody needs to immitate George Shuffler exactly, note-for-note. His cross-picking in the early days with the Stanley Brothers was rather simple compared to the competition virtuocity of David Grier, Tony Rice and others.

You can work on your own version by immitating fingerpicking pattens with the flatpick. You should be able to include any one of the six strings in any order you want, a bit of a practised skill. It sounds like fingerpicking except that only one note sounds at a time, but the notes can be loud and clean.