You are on the right track. My wife tought our Koi to eat out of her hand by holding her hand in the water with food. You want to hold the food so that the fish can see and smell it. If you don't let go of it, they will soon figure out that they need to come and get it. If they don't eat it, don't let them have it. It sounds cruel but after a day or so they will learn if they want to eat they have to get it from your hand.
