We used a Daisy BB gun. Shot them just behind the head in the center. They never flinched, little white hole the size, of, well, a BB. They were small frogs, and you could use the legs, and cast what was left in the Lilly pads on a jig, a catch a bass or two.
In later years, we netted them, and sold them, live, to a bait store.

Best,
Ted