First tug on the reins and say Head Up! Then start tapping on her shoulder and keep tapping quicker and harder until your are about slapping her neck if you need to, her head will come up, then rub her out and ask her to walk.
I hate when people don't think bitlesses don't work! Like when they say "Those things don't give you enough control" As if you can ever CONTROL a horse! The horse is trained to give in to pressure. If he can be trained to respond to pressure in his mouth he can certainly be trained to give into pressure on his nose. Whitney is not an easy horse to ride. She likes to bolt and try to take off and sometimes rears and bucks. Definitely wouldn't put a kid on her. If she can work in a bitless, any horse can.
I couldnt agree more! Regardless if you have a bit or not if the horse doesnt want to listen its not going to.
As for the trying to eat. Hmm. What I did with my boy....since if he eats just once he thinks he can do it every time and boy will he try...... I use a very growly voise, and like what Chicalove said a jerk with one rein. And to make it more effective do it before he gets his head down. And make sure you keep riding him forward.