Fr. William Most has written well on this subject. If you search the EWTN library you will find several of his articles about effiacious grace, sufficient grace etc. He certainly raises many valid points against common interpretations of Aquinas.
**Ordinarily, grace can be resisted, but a number of theologians say that there are extraordinary graces that infallibly produce their intended effect, though without destroying free will. How this works, I do not know… and if I somehow could, I doubt it would be easy to explain! :**D
In his work, ‘Grace, Predestination and the Salvific Will of God,’ Fr. William Most provides the following anecdote, which I believe is as far as most of us should probe into this intellectually exhausting topic: "One day, when the thought of the mystery of predestination caused St. Rose of Lima to fear greatly, Jesus said to her:
'My daughter, I condemn only those who will to be condemned. Therefore, from today forth banish from your mind all uneasiness on this point.’ "
St. Alphonsus does not go into great philosophical depth about the topic of predestination, but he does indirectly provide an alternative to (in)sufficient and efficacious grace:
catholictreasury.info/books/prayer/pr16.php (This is a good read!)