The Great Compassion Mantra and 42 Hands and Eyes are specialized Dharmas for Great Master Xuan Hua’s llineage. They bear the very heavy burden of propagating Mahayana and therefore need these types of specialized Dharmas to facilitate their work.
The Hands and Eyes are a Secret School Dharma and must be transmitted before it can be cultivated. Nowadays, only a few of Great Master Xuan Hua’s most senior disciples are authorized to transmit this Dharma. You can find publications and other materials on the Internet about this Dharma. However, you should not cultivate it. Why not?
Allow me to emphasize again: do not practice this Dharma unless you have received transmission from a senior sanghan from the DRBA’s big wigs. As far as I know, they rarely transmit this anymore. There is no need to be greedy. If you have the potential, you will eventually be able to receive transmission.