If I'm remembering correctly, Scott was catching those giant cats from a small lake in the Omaha area. There were automatic fish-pellet feeder(s) there. Since the pellets tend to float for a while before sinking, the fish were coming to the surface to eat the pellets. You might want to use an UNWEIGHTED woolly bugger in that situation, so it will have a much slower sink rate. Cast to feeding fish.
At most other places, like where I fish, it's a game of chance. Although I've caught some really big cats during the middle of the day, most of them come just after dark. This is when they start cruising the shallows looking for food. Keep a fly in the water, moving slowly...eventually you will cross paths with a catfish. I've never tried adding scent to a fly, but I will admit I've tried "chumming" an area with bread to get the catfish to feed near me. Sometimes it works, sometimes it doesn't.