To be in control of either of these implements was a pretty big gig for an altar boy!
The thurible ( incense holder and swinger ) is still used in liturgical celebrations as are the bells but at Benediction they came into their own. The thurible was loaded just before the Priest ascended the stairs of the altar to approach the monstrance and elevate it in blessing for the congregation. Father would give it a good swing or two at the start of this process and then hand it to the altar boy who would maintain the swing throughout the duration of the blessing. Incense fumes, depending on the heavy handedness of the Priest could take out every asthmatic within 30 feet, making eyes water and throats close!
The Bells were used at every Mass – the warning bell, the bell for the elevation of the host, the bell for the elevation of the chalice and the time to get ready for communion warning bell. Heaven help the altar boy who missed a bell or who rang the bells too long or who couldn’t get the “donger” in the bells to work properly making the bells sound insipid in the extreme. The biggest gig for the ringing of the bells occurred on Holy Saturday night when The “Gloria” was sung ( Gregorian chant of course) for the first time since the beginning of Lent. This usually took about 5 minutes and the altar boy had the incredibly important job of ringin’ those bells from start to finish!
As an aside, the tradition of ringing the bells at Mass started with nothing to to do with reverence or respect. In fact it happened because of lack of reverence and respect. Hundreds of years ago in the big Cathedrals where Mass was said in Latin and all the action was restricted to around the altar, people used to gather, get bored and chat, do business etc. As a means of settling the din to let people know that communion was approaching bells, not little ones but great big clangers, would be sounded as a means of getting them to shut up, pay attention and look at the raised Host and Chalice! Crowd control has always been an issue!
Benediction provided a good sort of partial practise for Holy Saturday night because the bells had to be rung from the time the priest lifted the monstrance and made the sign of the cross ( usually three times for those on the left, those in the middle, those on the right of the congregation) and turned around and place it back on the altar.
One of my sons who has been free range in his catholicity since in he was in year 10 and is now 43, hovering on the cusp of 44, attributes his highly successful career in theatre, specifically lighting and stage design to the theatrical immersion in the Catholic Faith “forced on him” by family history!