It is a lot like stripers. Live or Chunks. I am only in my second season for flatheads and all the local "experts" said it has to be live bait. Much like a big bass they get lazier with age and look for easier meal. All my big ones come on chunks that I give a good squeeze.
I also apply striper tactics on the water i i fish I like rip water or rocks, most people will fish where it is comfortable for them , i.e no snags dont have to wade etc, there is a big sub society of guys after these fish and I was able to sling shot past a lot of them using striper knowledge.