According to the preface, what is considered the most effective form of Guru service through writing?

The most effective and certain service in writing that is said to grant the fruit of salvation is to write the biography of one's Sadguru. As detailed in Chapter 0, this should be done either by the Guru's command or through inner inspiration. This service involves not just writing but also personally studying the biography regularly. The text emphasizes performing hundreds of readings (Parayans) and weekly recitations (Saptahs) with a pure heart, unwavering devotion, and selfless love. This form of service, which is of the body and speech, is considered superior because it can be done without interfering with one's family or worldly responsibilities.