first, Geshe Tsephel is my teacher.
The retreat which I received this empowerment for this practice was 7 days long. The commentary of this book provides supports for the short and middle lengths sadhanas by explaining the middle length. The commentary fills the gap between the sadhana and the actual practice. The commitments for this practice is 6 Guru Yoga Sessions a day. Different teachers have different requirements. It is highly recommended to have and do Vajrasattva purification (or Nungdro) practice for a couple years before receiving this empowerment. Allot of difficulties are removed by receiving the empowerment. Without it, the book will be very confusing and difficult to read n understand. Lastly, please get the empowerment before reading this excellent book. This book points the way to enlightment but the Guru is the start and finish of enlightment.