As that is a Swyama Siddha Hanuman Mantra it doesn't have to generally be chanted for a fixed amount of Mantra Repetitions for being able to use it. Exclusive worship and rituals and guidelines about route, sitting mat, and counting rosary are certainly not recommended for chanting this Hanuman Mantra. https://www.youtube.com/watch?v=ufkmD95y7fE&t=32s