The number of
ducti used during the liturgy is not as specifically explained in the current Ordinary Form of Mass as it is in the Extraordinary Form, and part of this ambiguity seems to stem from the rather loose translation of the Latin original made for the English edition. First, let us look at what the current liturgical books say, in English.
The current GIRM says in number 277:
"277. The Priest, having put incense into the thurible, blesses it with the Sign of the Cross, without saying anything."Before and after an incensation, a profound bow is made to the person or object that is incensed, except for the altar and the offerings for the Sacrifice of the Mass.
"Three swings of the thurible are used to incense: the Most Blessed Sacrament, a relic of the Holy Cross and images of the Lord exposed for public veneration, the offerings for the Sacrifice of the Mass, the altar cross, the Book of the Gospels, the paschal candle, the Priest, and the people.
“Two swings of the thurible are used to incense relics and images of the Saints exposed for public veneration; this should be done, however, only at the beginning of the celebration, following the incensation of the altar.”
The other authoritative liturgical book, the Ceremonial for Bishops, says in number 92:
"The censer is swung back and forth three times for the incensation of the **lessed
acrament, a relic of the [T]rue [C]ross and images of the Lord solemnly exposed, the gifts on the altar, the altar cross, the Book of the Gospels, the Easter candle, the bishop or presbyter who is celebrant, a representative of the civil authority in official attendance ata liturgical celebration, the choir and people, the body of a deceased person. **
“The censer is swung back and forth twice for the incensation of the relics and images of the saints solemnly exposed for public veneration.”
The problem is that the terms used in both the GIRM and the CB are: a) liturgically speaking, somewhat vague, and b)not very precise translations of the Latin. This short article, which I strongly encourage you to read, explains the issues, and how an attempt at interpretation and clarification inevitably leads one back to the old rubrics. dcgb7f.wordpress.com/tag/incensation/
As for intepretations of the rubrics, I believe that you are familiar with Bishop Peter Elliott’s Ceremonies of the Modern Roman Rite, which is the main rubrical guide for the Ordinary Form, filling the same role as Fr. Adrian Fortescue’s Ceremonies of the Roman Rite did for the Extraordinary Form back in the pre-Vatican II days. Here is what the then-Monsignor Elliott says in 217-218:
"217. There are two kinds of swings or ‘ductus’. To make a double swing, the thurible is swung twice at the person or object to be incensed, and then lowered. To make a single swing, it is swung once and then lowered, except when incensing the altar, when the single swings are made continuously as the celebrant walks around it.
“218. The customary rules governing these different forms of incensation are as follow: (a) three double swings are made to incense the Blessed Sacrament, a relic of the Cross, images of Our Lord set up for veneration, the gifts on the altar, the altar cross, the Book of the Gospels, the Easter candle, the celebrant (bishop or priest), a representative of the civil authority officially present at a celebration, the choir, the people and the body of a deceased person. (b) two double swings are made to incense relics or images of Our lady and the saints set up for veneration…”
And yes, the CB says that the deacon incenses the people. Neither the CB or the GIRM say who is to do this if there is no deacon present, so one presumes that this would be done by the thurifer himself.
Long story short: I would recommend following Elliott’s interpretation, with three doubles for the Blessed Sacrament, as well as the celebrant, etc. I would give a deacon two doubles. Traditionally the book of gospels and groups (multiple altar servers, the congregation) would get three singles (center, left right), but the current rubrics do not provide for that, so I would follow Elliott’s guidelines.