Hilchos Maasei Hakarbanos 9:14

If a kohein brings a thanksgiving offering, the rest of the bread is eaten by the owner just like a thanksgiving offering brought by a Yisroel. This is because the bread that is brought with a thanksgiving offering or the ram of a nazir is not considered a flour offering.

Hilchos Maasei Hakarbanos 9:15

If two people jointly bring a peace offering, one of them waves it with the other’s consent. Even if 100 people bring it jointly, one waves it on behalf of all of them. This is different than the procedure for the laying of hands.