375. A Minyan of Kohanim

Tefillah u’Birkas Kohanim 15:8

Anyone standing behind the kohanim is not included in the blessing; those standing at their sides are included. If there’s a partition - even a wall of iron - between the kohanim and the congregation, they are still included in the blessing because they are facing the kohanim.

Tefillah u’Birkas Kohanim 15:9

Birkas kohanim is only recited when there is a minyan of ten. The kohanim can be counted toward the minyan. If a shul happens to be composed entirely of kohanim, they should all duchen. So who do they bless? Their brethren in the north and the south. Then who responds “Amen” to the blessings? The women and children. If there's more than a minyan of kohanim, ten should respond “Amen” and the rest should duchen.