Hunting catfish is different than hunting other types of fish. The techniques are more important after you shoot than before. Flathead catfish have a very tapered head and almost any shot on the skull will bounce off. You need to get a deep hit near the spine and get a flopper behind a bone, the fish has the power to rip out huge areas of flesh, if they can fight at the end of a line.
When you get a hit, jump on top of the fish and push it into the bottom, or pull the fish into your body and clamp your legs around the tail. Now while you're holding the fish get a stringer through the mouth and out the gill. If the fish is in a hole, often it will be head on, and any attempt to shoot it in the mouth, will be too slow and bounce off the flat head. Flick a light beam in and out of the eye till the fish turns to give you a shot. Reach into the hole and grab the lower jaw, hold tight. If the catfish can shake it's head back and forth, you'll lose some skin....
Also, if you haven't learned before, Flathead catfish change color to blend into the bottom, where they are hunting. When hungry they may be sitting on the bottom in the middle of small bait fish, waiting for a larger prey. After, they've fed they will hold up where they can hide, under trees and roots, or in rocky holes.