Here's a pretty good method I've used on lions, scorps, and works on just about any gulping type. First get them eating gutloaded ghost shrimp (cyclopese is a good suppliment). Then start using a feeding stick with a live shrimp on the end (wiggle the feeding stick so it it enticing and the fish forgets about this stick). Once they are readily taking live feeders from the stick, feed a live one, then a dead one (thawed krill is about the same size.) The first few times the prepared food will probably get rejected, but eventually they will not care. After they accept the thawed krill, you can switch them to silversides or whatever you wish.
While using this method, it is important to feed 2 or 3 times a week max, as the fish must be good and hungry to take the risk of approaching the stick, and to aggressivly feed from it. I've used this method on the following fishes, some of which are notoriously hard to switch over:
Volitan lion
antennata Lion
Dwarf Zebra Lion
Fu Manchu Lion
sebastapistes cyanostigma (turn off lights for this species)
Taenianotus tricanthus, Leaf fish
Friends have used it on the following species with success:
Fuzzy dwarf lion
radiata lion
Rhinopias frondosa, aphanes, & eschmeyeri
diabolus scorpionfish
verrucosa scorpionfish
Anglers (frogfish) - commersoni, hispidus, striatus, maculatus
Sargassumfish Histrio histrio