You can do this Shabar mantra chanting for 11, 21, 31, or 41 days, the place and time of mantra chanting should be a similar for the volume of days you should do sadhana. You can use Rudraksha or Tulsi rosary to chant the mantra. It is actually mandatory https://sanskritmantras30656.blogproducer.com/39187891/new-step-by-step-map-for-most-powerful-sarv-karya-sidh-shabar-mantra-karya-siddhi-shabar-mantra-most-powerful-shabar-mantra