We have already looked at the Little Office of St. Joseph and the Litany of St. Joseph, both enriched with partial indulgences. In addition to these, we find the following text in no. 19 of the current Enchirdion:
A partial indulgence is granted to the faithful who invoke St. Joseph, spuose of the Blessed Virgin Mary, with a duly approved prayer (e.g., Ad te, beate Ioseph).
The particular prayer mentioned by way of example is provided here:
To you, O blessed Joseph, do we come in our tribulation, and having implored the help of your most holy spuose, we confidently invoke your patronage also. Through hat charity which bound you to the Immaculate Virgin Mother of God and through the paternal love with which you embraced the Child Jesus, we humbly beg you graciously to regard the inheritance which Jesus Christ has purchased by his Blood, and with your power and strength to aid us in our necessities. O most watchful Guardian of the Holy Family, defend the chosen children of Jesus Christ; O most loving father, ward off from us every contagion of error and corrupting influence; O our most mighty protector, be kind to us and from heavven assist us in our struggle with the power of darkness. As once you rescued the Child Jesus from deadly peril, so now protect God's Holy Church from the snares of the enemy and from all adversity; shield, too, each one of us by your constant protection, so that, supported by your example and your aid, we may be able to live piously, to die in holiness, and to obtain eternal happiness in heaven. Amen.
The prayer was composed by Pope Leo XIII, and can first be seen referenced in his encyclical, Quamquam Pluries no. 6. The prayer was originally intended for use after the Rosary (hence the reference to "having impored the help of your holy spouse"). In the last pre-Vatican II edition of the Raccolta, the prayer is indulgenced for "3 years" generally, but "7 years" on Wednesdays or after the Rosary during October. This latter point indicates to me that it was early used independently of the Rosary. Nevertheless, it is probably best said after the Rosary, both on Wednesdays and during the month of October.
There are additional prayers to St. Joseph which we might consider to be "approved" by the Church. In this regard, I would look to what is said in the Directory of Popular Piety no. 222.:
St. Joseph plays a prominent part in popular devotion: in numerous popular traditions; the custom of reserving Wednesdays for devotion to St. Joseph,popular at least since the end of the seventeenth century, has generated several pious exercises including that of the Seven Wednesdays; in the pious aspirations made by the faithful(305); in prayers such as that of Pope Leo XIII, A te, Beate Ioseph, which is daily recited by the faithful(306); in the Litany of St Joseph, approved by St. Pope Pius X(307); and in the recitation of the chaplet of St Joseph, recollecting the Seven agonies and seven joys of St. Joseph.
Of these, the most common form of the devotion of the Seven Sorrows and Seven Joys of St. Joseph are found in the Raccolta no. 470. I'm certainly no canonist, but I would imagine this to constitute "approval." The reference to "Seven Wednesdays struck me as odd, and probably referring instead to the "Seven Sundays of St. Joseph" (it doesn't look like the document received the best proof-reading, as evidenced also by the misspelling of the Ad te, Beate Ioseph).
Additionally, the prayers to St. Joseph before and after Mass in the Roman Missal could probably be considered approved as well. While these prayers might primarily be in place for the preparation of the priest, they are certainly suitable for the use of the faithful as well.
While prayers and devotions to St. Joseph are generally considered best during the month of March and Wednesdays, we might also consider at least some of them appropriate also during Advent. It is my opinion that they could enhance devotion especially to the Incarnation, whose celebration is anticipated in this season. As the season also includes the celebration of the Immaculate Conception of the Blesssed Virgin Mary, some devotions to St. Joseph may give a fuller sense of the Holy Family during this time, and the preparation for the celebration of the Nativity of the Lord.