After writing a short piece using this idea I would like to highlight a few points that I found to be kind of unique.
Choosing the Modes
Since the technique uses two different modes picking them and noting the similarities and differences between them. Picking two modes that are very close in what notes they use kind of defeats the purpose of this technique.
In my piece I decided to use the Lydian and Phrygian mode. Between these two modes, all 12 notes are used, but there are only two notes it common the root and the 5th. Because of this though, I had to be extremely careful with what notes were
Introducing the Modes
The two modes being used are at the heart of this techniques and thus it is vital to make sure that each voice has the mode it's using has to be established. A simple monophonic motive in each voice to highlight the mode was extremely useful.
Use of Imitation
To bring out the difference between the two modes playing one motive in one voice and then repeating it in the other helped highlight the differences between the two modes.
Use of "Dual" Haromny
There were many times that I would introduce duality in harmony. One simple example is for one beat the two voices would line up to make a I chord, but then with a voice exchange the chord would change into a i chord highlighting the difference in a very interesting fashion.
Cadences were at times tricky since the harmony didn't always allow typical cadences. With the Lydian and Phygian modes I found the Lydian voice using the leading tone and the Phygian voice using the mode to use the supertonic to approach the tonic. Other mode combinations may yield various odd cadences.