The Twenty-Third Zen Patriarch Haklenayaśas, named as Little Saint and Little Bodhisattva by many, became a monk at the age of 20, and practiced diligently in the mountains forests for nine years but didn't attain anything. He didn't attain the Tao until he met an enlightened master. Therefore we know that we don't need to practice hard or go retreat for many years in order to attain Buddha nature. We should have an enlightened master to get the key. It's no use no matter how many years or what method you practice. Only after we truly have Quan Yin Method and get the key can we benefit the sentient beings as well as ourselves.
The Twenty-Fourth Zen Patriarch Reverend Simhabodhi had been a Bhiksu for many lifetimes. He could even go to Dragon's Palace to recite Buddha's Sutra, but could not be liberated from life and death, because he didn't attain the method of liberation - the Quan Yin Method. Therefore we know that the Quan Yin Method has the greatest power. The Proper Dharma Eye Treasury is the ultimate method. That's why Master just told you to practice the Eye Treasury and not to exercise other body centers which are useless. We should practice the method of Tathagata Eye Treasury in order to attain the Tao.
If we want to be liberated from life and death and become Buddha, we have to depend only on the Sound. The sound stream is what brought us down here from above. Now that we have entered the path, we should let the sound take us up. Only great enlightened masters have the key to this path. Without enlightened masters, we have no way to enter into this sound stream, because there are many door keepers who will drive us away; but if we know an enlightened master, they will let us in, because now the Master can be our guarantee.