[HeidiLee]

I've been told by a trainer that it's best to remove the food as a lure as soon as the dog can do the trick without it. Sooner the better. You still use it as a reward but if it's a lure the dog will learn not to perform unless you have a treat in your hand. It's good to do a hand signal along with the command, even when you don't have a treat in your hand. Every dog's different but that's what I was taught.

From my experience with the one dog that I have, he learns the sign language faster than the audible command.