I heard that Master Xuan Hua stated that to maintain the Great Compassion Mantra without practicing the 42 Hands & Eyes Dharma is like having hands without feet.
I also understand from his explanation that one should not practice the Hands & Eyes Dharma without receiving official transmission. In that case, if I were to maintain the Great Compassion Mantra alone, what effect would it have?
Could you please explain how I should maintain the Mantra?
You should start first by reciting the Great Compassion Mantra. That will help you accrue blessings. When you have enough merit and virtue, conditions will arise to help you receive transmission for the Hands & Eyes Dharma.
The proper foundation for the Great Compassion Mantra Dharma is to become a vegetarian and keep the Five Precepts.
Do not lie or else you will not be able to practice the Hands & Eyes Dharma.
It is best to seek a Good Knowing Adviser in order to receive the proper guidance and protection when it comes to practicing Tantric Dharmas.