Jesus used mud and spittle to heal the blind man, as God he did not need to use anything, or lay His hands on anyone, or do anything but will that something be done or undone. However He did show us that we can and do use physical things to access the Graces God dispenses.
After Jesus’ Asension we see that the scarves (some translations hankerchiefs) of the Apostles were laid on people to bring about healing, St. Peter’s shadow cast upon the sick was cited as being used in the healing of a paralytic.
God commanded that the brazen serpent be fabricated and that anyone who looked upon it who had been bitten by a viper be healed. He did not need to use it, He rather could have said, call upon my name, your faith will heal you. But He required an act be preformed to obtain the grace, an act that included the use of a graven image, which was not worshipped but was utilized by God to bring about the healing.
So while physical items are not the source of the Graces they can be used by God to bring about His Graces when properly utilized.