An individual whose friend has not blown shofar may blow shofar for them etc. This is a baraita in the second chapter of Tractate Rosh HaShana (34b): "An individual whose friend has not blown shofar may blow for them and an individual who has not made a blessing, their friend may not make a blessing for them." And the RA"N wrote, "'Their friend may not make a blessing for them,' meaning that although we say that all of blessings, even though you have already made them, you can still make them for others, they already excluded from this rule, in Tractate Berachot, in the Jerusalem Talmud, the blessing after meals, and the reading of Shema and the daily prayers. And the reason for the daily prayers is because it makes sense that everybody should ask for mercy for themselves. However, this refers to a person who knows how to make the blessing. But if they do not know how to make the blessing, their friend can make it for them. As it says in the chapter, "Three who ate together"(45a), "If one is a scholar and one is an ignoramous, the scholar makes the blessing and the ignoramous get's credit." And this is written in the Mordechai and in the Haghot Asheri at the end of the first chapter of Tractate Rosh HaShana. And this is not according to the position of the RI"Z Giat and Rav Shrira which our Master (the Tur) wrote.