Giving Your Dua Over to Salawat
اللَّهُمَّ صَلِّ عَلَىٰ مُحَمَّدٍ وَعَلَىٰ آلِ مُحَمَّدٍ وَسَلِّمْ
Allahumma salli 'ala Muhammadin wa 'ala ali Muhammadin wa sallim.
O Allah, send blessings upon Muhammad and upon the family of Muhammad, and grant him peace.
What it means
Ubayy ibn Kab used to set aside part of his night for dua and asked the Prophet ﷺ how much of it he should give to sending blessings upon him. Each time he offered more, the Prophet ﷺ said it would be better for him, until he offered all of it. This is the dua you make when you do not know what to ask for, or when you are too tired to ask.
When and how
When you are weighed down and cannot find words, repeat salawat instead of trying to compose a dua. Set a count, such as a hundred, and keep going.
Its virtue
The Prophet ﷺ told Ubayy that if he devoted all of his supplication to sending blessings upon him, his worries would be taken care of and his sins forgiven, reported in Jami at-Tirmidhi 2457. The wording here is one of the common forms; any authentic salawat achieves the same.
Source
At-Tirmidhi 2457 (devoting one's supplication to salawat)