After marking one`s body with tilaka, a devotee should perform the Kirita-mantra-nyasa on his head so that he can achieve all perfection.
The Kirita mantra:-

Om srikirita-keyura-hara-makarakundala-cakra-sankha-
gada-padma-hasta pitambaradhara srivatsankita-vaksah sthala
sri bhumisahita svatma jyotir diptikaraya
sahasraditya tejase namo namah.

Translation.
I offer my repeated obeisances unto the Supreme Personality of Godhead, Who is decorated with a crown, armlets, necklace, and fish-shaped errings- in Whose Hands are held a conch, disc, club, and lotus-Who is dressed in bright yellow garments- Whose Chest is decorated with the mark of Srivatsa-Who is surrounded by His energies, Sridevi and Bhumidevi-Who is greatly effulgent-and Whose transcendental body glows like thousands of suns.
(Sri Hari Bhakti Vilasa).

In the Padma Purana, The Supreme Lord said, "O brahmana, while worshipping Me in the morning and evening, while performing a sacrifice, or simply for his own auspiciousness and protection, my devotee should mark his body with tilaka every day. Marking of the body with tilaka destroys all fear."
(Sri Hari Bhakti Vilasa).

In the Skanda Purana, it is stated, " A person whose forehead is decorated with tilaka made from white clay is pure, even if he is born in a family of dog-eaters. Such a person will surely attain the lotus feet of the Supreme Lord. Sri Lakshmi resides in tilaka, fame and liberation, and Sri Hari also personally resides in tilaka.
(Sri Hari Bhakti Vilasa).

In the Padma Purana, it is stated, " The beautiful space between the two parallel lines of tilaka is the residence of Sri Lakshmi and Sri Janardana, the Lord of Lords. One should know for certain that the body marked with tilaka is a sanctified temple of the Supreme Lord."
(Sri Hari Bhakti Vilasa).

In the Brahmanda Purana, it is stated, " One should decorate his forehead with tilaka while looking at his face in a mirror, or in water, but one should never touch the tilaka with his fingernails."
(Sri Hari Bhakti Vilasa).

" Round tilaka, crooked tilaka, tilaka without a space between the two parallel lines, short tilaka, tilaka that is too long, thin tilaka, messy tilaka, tilaka with the upper ends joined, tilaka in the wrong place, old and dirty tilaka, tilaka having a bad odour, tilaka applied with the left hand, and tilaka applied by some means other than using the prescribed finger are all useless."
(Sri Hari Bhakti Vilasa).

" Tilaka that begins from the nose and extends to the hair of the head with a beautiful space between the lines is considered to be a temple of Lord Hari. Lord Brahma resides on the left side, Sadashiva resides on the right side, and Lord Vishnu resides in the middle of the tilaka. One should not apply anything in the space in the middle of the tilaka."
(Sri Hari Bhakti Vilasa).

" One should begin applying tilaka from the tip of the nose and go up to the top of the forehead, using a suitable clay. The tip of the nose actually means three-quarters of the way down from the bridge of the nose. One should form two parallel lines, beginning from the middle of the eyebrows and moving upwards."
(Sri Hari Bhakti Vilasa).