The custom of such guhya or secretive Bhairava can be an oral custom that is continuing from the guru disciple custom. Their karmakand rituals and methods are mystery, they don't seem to be written down but only learnt and practiced in guru disciple custom. Kāla Bhairavaācāra is usually a karmakaand https://jasperulctj.blogkoo.com/a-simple-key-for-bhairav-unveiled-49738418