There is a Layman's blessing. It is something like:
Through the prayers of our Holy Fathers, Lord Jesus Christ, our God, have mercy on us (me). This can be said in place of the priest's exclamation, for instance, after the Lord's Prayer.
In the Greek Church I attend a pious lady often "follows on" aloud; this does distract me somewhat from trying to "follow on" silently in English but I say nothing. She is a dear friend and one of the yia yias mentioned below.
Regarding Troparia and Kontakia during Liturgy, in Russian practice this is almost always exclusively chanted by our choir, except when the Bishop serves when he leads the altar clergy and servers in the festal kontakion. In the Greek church I attend, the priest repeats the main Troparion after he has entered the Royal Doors, after which the choir repeats it again a third time, followed by other Troparia and Kontakia. The priest always intones the Theotokion.
The Unabbreviated Horologion of Jordanville in English tells us in the Prayers in the Refectory chapter my edition p. 209) the following:
_Priest (Abbot, Abbess)_: O Christ God, bless the food and drink of Thy servants, for holy art Thou, always, now and ever, and unto the ages of ages.
Since an abbot is not always and an abbess never a priest, this indicates that this and similar blessings may be prayed by the lay faithful.
The Greek yia yias here in Melbourne always say this blessing before a meal.
Also, if I as a nun am asked to bless or pray anything other than before a meal, I often read from Numbers 6:24ff.
What is the opinion of our priests on this board?