Puti's Immortality method

So Sun Wukong was one of Puti Zushi's students after leaving his homeland to find immortality. Puti taught Wukong his method of immortality in secret from the rest of his students, which the heavens did not agree on.

But how does Puti's immortality method work? Like, wukong's second method of immortality was crossing his name out of the letter of death. This obviously makes him immortal since now death won't try to find him. The other methods mostly involved consuming something (the immortal peaches, heaven's wine, and the guords of immortality pills).

Those are easy to understand why wukong gained immortality, but how did puti zushi teach wukong immortality? Like, what are the specifics of it?