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.
Joyful in hope, suffering in tribulation, be thou constant in thy prayer.
Benedictis, qui venit in nomine Domini. Osanna in excelsis.
"Blessed is he who comes in the name of the Lord. Hosanna in the highest!"