I have a vague memory of seeing books, maybe both in Hindi and English, on the chayapurusa, from the popular publishers in Dariba Kalan in Delhi, that seemed to be about some form of hypnotism or creating by visualization a being that would act for one's purposes. Unfortunately I didn't purchase any such. The only book with the word in the title that I find on WorldCat is Rajesa Diksita, "Devī, devatā, Hanumāna, chāyāpuruṣa, evaṃ Yakṣiṇī-Bhairava siddhi ke prayoga," Dillī : Dehātī Pustaka Bhaṇḍāra, [1974]. WorldCat seems to have a new format which I haven't had time to decipher and I am not clear whether there is actually a copy of this book in any library or not. The fact that the chayapurusa is something in or over which one may
obtain siddhi makes me think that it is not just a form of divination.
Allen