I say, and with God's success: Tayammum consists of two strikes: one strike for the face, and one strike for the hands up to the elbows. He strikes his hands on the ground, then brings them forward and backward, then shakes them off, then wipes his face with them, then strikes his palms on the ground a second time, bringing them forward and backward, then shakes them off, then wipes the outer and inner parts of his arms up to the elbows. He wipes with the inner part of four fingers of his left hand the outer part of his right hand from the fingertips to the elbow, then he wipes with his left palm (without the fingers) the inner part of his right hand from the elbow to the wrist, then he passes the inner part of his left thumb over the outer part of his right thumb, and then does the same with his left hand. This is the closest to being cautious; as it avoids using the dust that has already been used as much as possible. See: Radd al-Muhtar 1: 230, and Al-Hadiyya Al-Alaiyya p. 36, and God knows best.