For large projects, many large and small agencies use supervisors to manage the
teams of interviewers.
Supervisors can help pull a team together, conduct briefings with
interviewers, monitor the number of completed interviews and sometimes do some
of the backchecking and administration.
Often Supervisors do not themselves do interviewing, although most are very
experienced interviewers. Sometimes where there are problems completing a quota
or where work needs to be redone, the supervisor will fill this role.
If you look at "Specialist Expertise" on the database (third column on the
search), you will see supervising/managing experience marked, so you can look
specifically for supervisors in the right area.