That's the type of gaff I used and a straight up jerk is the key.

I also used one of these hand gaffs to release fish caught on jigs.

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Get three or so wraps of leader around your forearm, slide the hand gaff along the line to the jig, hook the jig, keep the leader taught with your hand down, lift the gaff straight up, and shake the fish off.

It makes for an easy release with minimal damage to the fish.