A blessing is a grace. A priest give the blessing at the end of Mass to all with the instructions to go forth and live the Gospel. His blessing “empowers” us to do our job better.
A father can (and should) bless his children, “empowering” them to fullfill their vocation as an obedient child.
Blessing an object (rosary, medal) etc is an outward sign demonstrating the real significance of that object. In a way, it “empowers” that object to do what it is meant to do.
All blessings are Christ-centered…and thus “empower” the person or object to do what they are meant to do. Without exception, everything we do should be Christ-centered. Thus the blessing includes the sign of the Cross and the invocation of the Trinity.