Tuning with harmonics has always seemed faster and more accurate, to me anyway, but you still have to start with at least one reference tuned string. After that, though it's pretty simple as long as you already know how to play harmonics. 5th fret harmonic to 7th fret harmonic from E to A string. Same with A to D and D to G. Then to tune the B do an open B string and the 7th fret harmonic on the low E. For high E use the 5th fret harmonic on the low E (6th string) to open high E (1st string).