Yes, Divine Grace can certainly help - in whichever form, call it Kali, Shiva, Christ, Angelic, etc. Mantra is one of the many ways to connect to the Divine, an effective way, not the only way.
While we can recite mantras, do spiritual practice, etc. Grace is not guaranteed. Abhinavagupta, a great Tantric master says - the nature of Grace is mysterious. If the whole thing was - I chant x amount of mantras and I get grace, there is no difference between the Divine and a shopkeeper, as this is not merely transactional.
That said, the Universe has been empirically known to reward sincerity and hard work, so the probability of Grace is certainly higher for those that actively seek it - through prayer, meditation, service, mantras, etc.
I had two students, one who recited a certain mantra of Krishna for decades and never felt any grace. Another one, a simple all-American housewife who was not even spiritual, but wanted a mantra as her arthritis was unbearable. A month later, she was smelling fragrances, hearing flute music, and her arthritis was gone! The other guy with decades of practice was flabbergasted. Why did this lady attain grace so damn fast - was it effort from previous lifetimes, was it the quality of her efforts, or intensity of her practice, hard to say! Grace indeed is mysterious 