Watch the Extended Perf./Breakdown 2 online guitar lesson by John Stowell from Modern Chord Melody

Extended Perf. Breakdown 2
To elaborate on the uses of melodic minor substitutions, melodic minor chords, scales and arpeggios can be used to create a variety of embellishments, extensions and tensions. For this tune, I employ the melodic minor in one of four keys over a dominant chord (as I mentioned in the previous video bank). The four keys are all modes of the melodic minor, a half step above being the super locrian (7th mode), a whole step below being the suspended flat 9 or dorian flat 2 (2nd mode), a 4th above being the mixolydian flat 6 (5th mode), the 5th above being the lydian dominant (4th mode).
I've had better luck internalizing these sounds in my own playing and teaching this material to students by thinking of the melodic minor in four keys over the dominant as opposed to using the concept of modes of the melodic minor. By slowly combining the original dominant scale/arpeggio with the melodic minor substitutions, you will be able to access the tensions (raised and lowered 5ths and 9ths) used over dominant chords. These sounds can be employed to move away from the original dominant harmony if the chord isn't functioning as a V chord, or to create resolution if the chord is part of a V-I resolution. Focus on each individual melodic minor key over the dominant and then apply the sounds in the context of a tune or short progression. In some situations, it could be appropriate to combine the different keys of the melodic minor to create a larger harmonic palette over the dominant chord.
For this solo, I'm focusing on some specific melodic minor substitutions over the dominant chords, based on the harmony of the tune. Because the A flat7#9#5 has two tensions, I concentrate on the A melodic minor (a half step above). The same theory would apply to to the B7#5#9 later in the piece (C melodic minor in that case).
For the G7#11, I would choose the D melodic minor (a 5th above). I'm not restricted to these harmonic choices, but they're a good place to start. Of course things can change if I'm interacting and responding to other players in a band.