Is it true that invoking blessings upon the Prophet eases the torment of the dead in the grave?

Praying upon the Prophet, peace and blessings be upon him, is among the best deeds and is recommended at the beginning of supplication. If the supplicant prays for the deceased and begins with praying upon the Prophet, peace and blessings be upon him, this is more likely to result in the supplication being answered. However, there is no specific evidence indicating that praying upon him removes punishment from the dwellers of the graves. Al-Sakhawi did not mention praying upon the Prophet when visiting graves at specific times. Rather, some mentioned it when the deceased is placed in the grave, citing a hadith (definition) that does not support this.