Blessing of Throats

In Paul Turner's Blog by Paul Turner

Q: After a Mass which included the Blessing of Throats today,  the pastor advised the deacon that the priests use the Sign of the Cross while blessing and that he understood that deacons, on the other hand, were to “impose” without including the Sign of the Cross.  

I can’t find any information about this, anywhere, so I have three questions for our favorite liturgist:
1.  Is that accurate? 
2.  If it is accurate, what is the correct gesture used to “impose”?
3.  If it is accurate, where can I find the rubrics on this?

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A: Look in the Book of Blessings 1628. A deacon blesses throats the same way a priest does. A lay minister recites the same words but does not make the sign of the cross over the person.