Tilak was part of Guru Gaddi ceremony when the next Guru was anointed.
Source:
The encyclopedia of Sikhism ,Harbans Singh.
gurbilas Chhevin Patshahi. Patiala, 1970
Bhalla, Sarup Das, Mahima Prakash. Patiala, 1971
Padam, Piara Singh, and Giani Garja Singh, eds.,Guru ban Sakhlari Patiala, 1986
Baba Budha applied Tilak/Tikka to five Sikh Gurus, from Guru Angad Dev to Guru Hargobind . Tikka was applied to the foreheads of 7th, 8th and 9th Sikh Gurus by Baba Gurditta Randhawa, grandson of Baba Buddha ji. This ceremony in the case of 10th Sikh Guru was performed by Ram Kanwar Randhawa alias Gurbakhsh Singh.
Source:
The encyclopedia of Sikhism ,Harbans Singh.
gurbilas Chhevin Patshahi. Patiala, 1970
Bhalla, Sarup Das, Mahima Prakash. Patiala, 1971
Padam, Piara Singh, and Giani Garja Singh, eds.,Guru ban Sakhlari Patiala, 1986