Based on the preface, what is considered the most effective form of Guru service through writing for attaining salvation?

According to the preface in Chapter 0, the best and most certain service in writing that grants the fruit of salvation is to write the biography of one's own Sadguru. This can be done either by the Guru's command or through inner inspiration. This service extends beyond just writing; it includes personally studying the biography regularly, performing hundreds of readings (Parayans) and weekly recitations (Saptahs) with a firm resolve, pure heart, and unwavering devotion. This service, which engages the body and speech, is also practical as it does not interfere with maintaining one's family or pursuing worldly prosperity.