Programmatically adding secondary and tertiary assignees

I have been adding the main assignee in my function assign_guide_id with add_filter( ‘wpas_new_ticket_agent_id’, ‘assign_guide_id’ ) however I need to add secondary and tertiary assignees. I can create these assignments in the wpadmin, but I have not had any luck creating thise in my wpas_new_ticket_agent_id filter function.

I have been trying to set meta data on the ticket posts with the keys _wpas_secondary_assignee and _wpas_tertiary_assignee set to my user IDs but this does not work in that filter.

Thanks for any ideas!