Where did Sai Baba get the Udi he distributed to his devotees, and how did he give it to them?

According to Chapter 33, Sai Baba would give Udi, which is ash, to all who came for his Darshan. This Udi came from the sacred Dhuni, a fire that burned constantly day and night in the Masjid. Baba would take handfuls of this ash and give it as a benediction or Prasad. The text describes how he would apply this ash, also called Vibhuti, to their foreheads with his own thumb and place his entire hand on their heads, wishing for the welfare of his devotees. This Prasad was distributed daily and without obstruction.