What does the text identify as the most effective and certain form of Guru service through writing?

According to the preface, the best and most certain service in writing that grants the fruit of salvation is to write the biography of one's own Sadguru. As detailed in Chapter 0, this service should be inspired either by the Guru's direct command or by a deep inner calling. It is a comprehensive practice that involves not only writing but also personally studying the biography regularly, performing hundreds of readings (Parayans), and conducting weekly recitations (Saptahs) with unwavering devotion and a selfless heart. This service of the body and speech is considered supreme and does not interfere with one's worldly duties.