Does drawing the sign of the Cross benefit the person drawing it or the observer?
The Christian draws the sign of the cross as a sign of his faith in the Holy Trinity: the Father, the Son and the Holy Spirit. With the sign of the cross, we confirm our belief in the incarnation of our Lord Jesus Christ, and our faith in the redemption and atonement through the cross. We also draw the sign of the cross on ourselves to protect us from the evil one and remind us of the power of the Cross in our life.
You can read more about the sign of the Cross at www.suscopts.org/messages/lectures/misclecture4.pdf.