You are able to do this Shabar mantra chanting for 11, 21, 31, or 41 days, the spot and time of mantra chanting need to be the same for the amount of days you want to do sadhana. You can use Rudraksha or Tulsi rosary to chant the mantra. https://dallaswrkcw.bcbloggers.com/31656589/what-does-most-powerful-sarv-karya-sidh-shabar-mantra-karya-siddhi-shabar-mantra-most-powerful-shabar-mantra-mean