You are able to do this Shabar mantra chanting for 11, 21, 31, or 41 times, the position and time of mantra chanting need to be a similar for the number of days you wish to do sadhana. You can use Rudraksha or Tulsi rosary to chant the mantra. https://wayloncgiik.blog-kids.com/32550188/considerations-to-know-about-most-powerful-sarv-karya-sidh-shabar-mantra-karya-siddhi-shabar-mantra-most-powerful-shabar-mantra