When to cross yourself is not prescribed by the church. What you mentioned in your original post, is the common recommendation of a priest. No one should be telling you when to cross yourself. Making the sign of he cross is part of your (our) personal, silent prayer. Cross yourself when you feel it, not when some know it all tells you to. I happen to cross myself at the mention of the bishops name, as that is my personal reinforcement of my own prayer for him and his work. There are two other petitions I cross myself at, which is my choice and not common. I have noticed in Russian practice, they tend to cross themselves at the "let us pray to the Lord," for each petition.