I use the spoon method, as Grif does. The best spoon I have found to do this is a zoo pals plastic spoon. They are smooth and thick so your frog can't crack them or get hurt.

I too though am wondering if we could help your frog get to eating on his own? Can you tell us more about him? Size of frog? Type of home? Temp and humidity in his home? Is he showing signs of illness or just not eating?