The נוהג כצאן יוסף writes,
"Those standing next to the Mohel say quietly (for the Mohel to hear) the end of the Bracha (על המילה) so to make sure
the Mohel doesn't ח"ו mistakenly end the Bracha with על השחיטה."
In most smaller communities they hired one person who was the Melamed teaching the children, the Shliach Tzibbur,
the Shochet, & Mohel.
The Bracha על השחיטה he made regularly whereas על המילה was done on rarer occasions.