Torah Temimah cites Menachos.
“He shall not put and he shall not give” — might one think the two prohibitions apply only when two kohanim act (one oil, one frankincense)? Scripture says “upon it” — the focus is the body of the minchah, so even one person who adds both incurs both lavin.
Diyuk of “aleha” versus agents — liability follows the minchah itself, not the number of people who touch it.
One kohen who places both oil and levonah on the chatas flour violates both negative commandments. Splitting the acts between two agents is not required for liability. The Torah’s language centers on the flour, not on the number of hands that touch it.