"We can agree that I will destroy the hair as soon as each hunting party is safely back at the covenant. I will ask if my son Merin could manage this business with the hair."
When he gets the list of willing hunters, he invites them all as well as his son Merin (if he agrees to do this) outside his laboratory. He will explain to them:
"Before we start, I will say that I am going to use this on you."
He raises above his head the tablet that shows personality traits, the one that Silas borrowed Lares here:
"It will give me information that helps me discern which of you are suitable for the hunt at this initial stage. If you are unwilling to participate, I will not force this upon you, but I will not consider you for the hunt at this point, but perhaps later."
He will then take each individual who stays aside and use the tablet on them in turn, making sure that no one sees what it shows. He will mark down everyone's name and personality traits, again keeping the information hidden from everyone.