Good vidhi should be to be followed though activating the mantra. According the Purohits, one have to chant minimum amount of 21 malas or 2268 instances accompanied by the chant of dashansh homam (i.e. 1 tenth of the full chants). Although undertaking the homam, remember to hold a kalash full https://www.youtube.com/watch?v=qnEcMQtKTvg