I don't have any direct experience on catching cats in the winter, but I think you're on the right track with chumming the area you're going to fish at.
You could also try scenting the bluegill chunks with some attractant.
Years ago in my previous manifestation of this pond and well before the renovation, that's how I would catch catfish, is by chumming first. Those were big fish back then and since have died out so this is an entirely new batch and one that I pellet fed through the summer.
I've always had a fun time trying to catch crappie, bass, and bluegill over the course of a few unseasonably warm days in the winter but never attempted to catch catfish in the winter. I'm itching to catch and eat a few. At least I got a batch of bluegtill cleaned up and am happy to see my Spring stocking already has some that reached handsize and are readily biting on the worms I dug out of my compost. A half dozen of those catfish though will stuff the whole family in one sitting.
