Horseshoe is privately owned all around the lake; the only area you can fish is from the road on the bend just south of the entrance to Boyd, and it is so low the bottom is showing. Forget Horseshoe for now.
In Boyd, I know of good cats caught in 4 places.
1. A guy sitting on the rocks at the end of the marina channel caught an 18 pounder last summer.
2. A lady fishing at the inlet from Heinricy Lake (but when the gate was open and water was running) also caught an 18 pounder. That's just south of the camp ground.
3. I watched a guy fishing in the pump house inlet channel with night crawlers who caught three 7-pounders in a row, last August. So far this spring, they don't seem to be in there yet, but I could be wrong.
4. If you fish Boyd at night, you can cast out from the shore at the south edge of the swimming beach and catch both walleyes and cats. They like night crawlers, but they absolutely love big crawdad tails, if you have a place where you can trap crawdads. This last spot was told to me but I haven't fished it myself.