Watch the November online guitar lesson by Stephen Bennett from Harp Guitar Repertoire
I have also played this with harmonics on the C and G sub-bass strings in the section. It's a bit tricky because they come at you kind of fast - but it is nice. Sometimes I do it this way, sometimes not.
Those harmonics would be achieved by finding the halfway point of the vibrating length of the string and using your index finger to touch the string there - while plucking it with the ring (or middle) finger. Remember that the location of the halfway (or octave) node on the sub-basses is not going to be a straight visual line - ala the way you can go straight across the 12th fret of the guitar. Because the length of the sub-basses varies, the node's location will vary accordingly.
Or – don't worry about it and just play it the way I'm showing you on the screen.