The custom of such guhya or secretive Bhairava is definitely an oral custom that is continuing while in the guru disciple tradition. Their karmakand rituals and tactics are secret, they aren't published down but only learnt and practiced in guru disciple tradition. From the Kala Bhairav Ashtakam by Adi Shankracharya, https://raymondywsle.blogunok.com/30343801/rumored-buzz-on-bhairav