Why a Latin Mass parish? My parish is a Novus Ordo parish and the Scapular is promoted here. It's not only Latin Mass parishes where such things are promoted.
If an average Catholic soccer mom went to an average sacristy and asked for this once average blessing, I do not even think the average Latin Rite cleric would know what in God's holy name she was talking about. In fact, what priest do you know who even has a copy of the prayer of enrollment?!
I respectfully disagree. Just about this time last year I asked my confessor (not a "Latin Mass" priest) to enroll me if I brought him everything needed. He said absolutely! At my next confession, I brought the formula, in both Latin and English, and holy water. He asked me if I wanted him to do it in Latin, and I said sure! A few weeks later, two friends of mine went to the associate pastor of a different parish (a parish which gets a little too creative when it comes to the sacred liturgy). The associate pastor is filled with Carmelite spirituality, and had the necessary formulas to enroll my friends. He had also commented to them that "something" was up, because more than one person had requested this of him in recent weeks. And this all happened in California!