No matter what the coating, I have found that substituting the egg/ milk wash for half and half is far better. Leaves a more uniform coating on the fillet and sticks better. Being a mix of milk and sweet cream, I think it adds to the flavor.
We prefer a dry coating on our perch, so we crush cracker crumbs, add flour and Italian bread crumbs along with typical seasoning. After dipping the fillet into the half and half then rolling in the dry mix, they are ready for the fryer. More cracker crumbs make for more crunch, less cracker crumbs for less crunch....fine tune to your taste.....