There have been a number of posts here about this topic, but I don't know that any jump out at me as being clear or definitive on training non-feed trained LMB. I know some folks have had real success with SMB, but not sure about LMB. I've had a single LMB in an aquarium for about a year now and he refuses to touch a pellet. Worms, crickets, grasshoppers, feeder fish - he'll take 'em all, but he refuses to touch a pellet. I've succeeded in training BG, but they're pretty easy since they seem to be the seagull of the fish world - if it's in front of them, they'll eat it.
I'm actually just starting to work on about 30 YOY BG that my wife and kids netted yesterday. We tossed them in to a little aquarium and I ground up some of the Burris feed I use in our pond and they seemed to go after it pretty well. If you start with YOY LMB in a tank and they get hungry enough, you may well be able to get them to take pellets. Let us know if you try it. I think that captivity paired with no other real food source is probably a good motivator to get them eating what you want them to eat, then transitioning them back to a pond may well lead to success with feeding. I doubt you can do it in the wild.