I have run a minnow trap in my creek to try and sample all of the various minnow species. Surprisingly, I caught yellow bullheads in the trap a few times.

There are lots of threads on Pond Boss about trapping fish in ponds. (I think they are usually for sampling or culling sunfish?)

I suspect in the right location and with the right bait, you could trap a lot of bullheads. (With a trap for catfish, not a minnow trap.)

As a kid I used to fish farm ponds for bass and BG. Some days we had poor luck. My grandfather would then take us to one of the muddier corners of the pond where the prevailing wind would push items in the pond. We might then catch a bullhead on a bit of worm with every single cast.

I don't know if that is the best spot to try a trap, but that would be my advice. Hopefully, some experts will drop in and give you better advice. I do know that bullheads can become a high percentage of the fish mass in a small pond.