As this can be a Swyama Siddha Hanuman Mantra it doesn't have being chanted for a hard and fast amount of Mantra Repetitions for being able to use it. Special worship and rituals and rules about way, sitting down mat, and counting rosary are usually not advisable for chanting this https://www.youtube.com/watch?v=ufkmD95y7fE&t=32s