I'll try to more succinct this time.
The practice of using guide tones is not unlike using digital patterns like
1235,3579, or 1353, as Coltrane did all over his Giant Steps and Count Down
solos. Practicing with guide tones is a way of learning to resolve
dissonances to consonances, resolving the b7th of the iim7 chord down a half
step to the 3rd of the V7 chord. This is also not unlike learning to
resolve a 4-3 suspension in a classical chorale, it is just a compositional
tool. Knowing this tool helps one to write melodic patterns over chord
changes and control there tension and release. Once the melodic pattern is
written down and the lick becomes part of your playing, you no longer think
of it as guide tones but as a lick or melody which you add to your personal
vocabulary.
Brian Oates