You either train the fish, or allow the fish to train you.
It's really that simple.
It's not rocket science, but there is some skill involved, and in some cases you need to have
great patience, and be smarter than the fish.
Using bloodworm juice is a natural for FH, the smell triggers a feed response, the pellet becomes more palatable because it is softer,
and the taste is very familiar to the fish. Even if the FH resists it initially, usually they will start picking at the pieces of pellet at the bottom of the tank. Once they start even eating small pieces off the bottom, you are on the road to success.
I've lost count as to how many wild caught fish I have trained to eat NLS over the years. Some take to it straight away, others are more stubborn and require some serious effort.
Discus are known as being very picky eaters, yet even those raised as fry & small juveniles on a diet of beefheart can be converted with a bit of effort. The discus below were raised in Germany on beefheart, and converted to NLS when they were imported as juveniles. This is what they look like after eating NLS exclusively for over a year. (photos taken at a local breeders fishroom)