Whether Ignatian spiritual exercises are good for the discernment of vocation according to Thomistic understanding of vocation? All I know about Ignatian spiritual exercises was orally transmitted to me from priests and others, therefore I may misunderstand Ignatian spiritual exercises and in that case please correct me.

According to this video and from what I hear from people around me, is that Ignatian spiritual exercises are good for the discernment of vocation (whether one should be married or live as a monk or become a secular priest) for one's life. In these Ignatian spiritual exercises, one should listen internally for some kind of spiritual movement of the soul that comes from Holy Spirit and based on these feelings discern what path in life to take. These movements from the Holy Spirit are conferring some grace to one's soul, but why believe that one should feel the receiving of grace? One typically does not feel grace, rather, it is perceived through a longer time by considering objectively one's life. From what I understand about these Ignatian spiritual exercises it seems to me that they just add to what solid Thomist Rev. Fr. Richard Butler O.P. calls "An Unnecessary Mystery".

Question: Whether Ignatian spiritual exercises are good for the discernment of vocation according to Thomistic understanding of vocation?

Some related questions that shed more light on the Thomistic understanding of vocation and which will help in understanding my question:


Catholic doctrine on spiritual vocation. 
History of the doctrine of a religious vocation in the Catholic Church.
Father Romanus Cessario, O.P.'s essay, Thomas Aquinas and Vocational Discernment may be of use to you.  There he argues that the Ignatian commentarial tradition deviates from a Thomistic understanding of grace and vocation.  For example:


  Aquinas does not encourage a man to practice a “discernment” of Dominican life in order to distinguish it from other possible vocations in the Church. The reason is simple. Growth in charity results only from a divine gift given. We call this gift, the gift of grace. Strictly speaking however, no one can discern a grace, no one may discover by human means whether or not he possesses sanctifying grace. The Church in fact disallows a direct knowledge of the presence of habitual grace in a given individual: “Since it belongs to the supernatural order, grace escapes our experience and cannot be known except by faith.” (29) Aquinas reasons as follows: God is the principle and source of all graces given. God, however, remains “beyond the reach of our knowledge on account of his sublimity.” (30) So no man can discern with certainty, that is, grasp, perceive, apprehend, or judge, that he possesses the gift of divine grace.


From what I remember, the gist of the article is that simple things guide discernment, such as love of God, a desire to serve him, and a free choice of the will.  For Cessario the tradition that has come out of Ignatius' Exercises is too complex and seeks out a kind of certainty that just isn't attainable or realistic.