From the Treasury of Knowledge in the fourth chapter of the eighth section called A Detailed Presentation of the Process of Meditation in Vajrayāna, Rinpoche explains mainly the root text for the Six Applications and the part of the commentary that relates directly to it.
Here, you also find two short recordings in Tibetan only, where Rinpoche prepares his translator for him possibly teaching on this subject in the summer of 1985.
2+6 talks, audio
Tibetan only, Tibetan - English