You can use a mantra, yes. I prefer to sublimate in the beginning of my practice, so as to establish the necessary energies for meditation. Then during the elimination process, after having comprehended a specific defect, we can then use a mantra to pulverize that ego. I have found that the combination of mantra with prayer, visualization, concentration and relaxation is exceptionally powerful, and makes of this retrospection meditation practice a true ritual to the Divine Mother.