Have you ever been at a Mass which ended with a Solemn Blessing? This is when the deacon or (in his absence) the priest says: "Bow your heads and pray for God's blessing." The priest then says a blessing with multiple parts, and the congregation responds "Amen" after each.
Of course... the congregation has their heads bowed, so they're looking at their folded hands, the back of the pew in front of them, or the floor. This means, even if the priest or deacon makes some sort of gesture signaling their response, they won't see it. Often people don't know when the phrase the priest is saying has ended. How can we resolve this?
Chant the Solemn Blessing. This is my request.
If you're a priest reading this blog, and you plan on using a Solemn Blessing (since the Sacramentary provides such blessings for Advent, Christmas, the New Year, the Epiphany, the Passion, the Easter Vigil, Easter Sunday, Paschaltide, the Ascension, and numerous other occasions), please, please consider chanting it. (If you're not a priest, please suggest this to your priests, or at least to your pastor. Refer them to this post.)
How can you do this, you ask? Well, the Sacramentary, in Appendix III - Music for the Order of Mass, on pages 1045-1047, provides two models for chanting the Solemn Blessing. For each of these two models it provides an example using the Solemn Blessing for Advent. Spend some time with it. If you use the same setting (A or B), your congregation simply needs to know the tunes for "And also with you" and "Amen", which are very simple.
I might provide audio clips, if the Spirit moves me.