This is what i did wit my gars. All four of them are now on pellets. So i now can say it works. I think its all about getting gar to realize that what you put into the tank is food apart from fish.
1) Buy some crickets
2) Buy a brown floating pellet. I use hikari bio gold.
3) Put some live crickets in the tank and watch them get eatten.
4) after a few days of feeding the cricket they will learn that if its brown and floats its food.
5) Mix the pellets with the crickets, and watch if he eats the pellets, he will take in his mouth and spit it out and maybe eat the odd one, this is gud as he is learn the pellets are food.
6)Cut down the number of crickets you feeding him , by now he sud be eating some pellet.
7) stop the crickets totally and just add pellets, he will go by them and push them around and will take some.
Thats how i got all my gar on pellets, now my small ones are eatting pellets and freeze dry shrimp daily.
Goodluck
Hope this helps you