If a kohen has a sore throat, and can not duchan. Can one be yozei duchaning through another kohen (Shomea ke’oneh)? If so, should he say the bracha to himself?
This question involves a dispute among authorities. According to the Beis Halevi, one cannot be yotzei with another Kohen; however, according to the Chazon Ish, one can be. I recall seeing in Sefer Reishis Bikkurim that upon journeying in a certain place, the author (Rav Betzalel Hakohen of Vilna) he encountered a custom of one Kohen being motzi the other, and was honored to be the kohen that says the blessing for others.
On account of the dispute, the kohen in question should ascend to duchan, and should ask one of the other kohanim to be motzi him both with the blessing before duchaning, and with birkas kohanim itself.
Of course, this should only be done in cases of a very extreme sore throat, in which the kohen is actually unable to speak.