I understand that you need patience with Treat training. but what if you don't have alot of time due to work ??? or not alot of patience either ???
you make time! training sessions do not have to hours long, actually its better to train for only a few minutes several times a day. for example, say your watching tv, when a commercial comes on take them couple of minutes to train.
also if you start to get frustrated take a deep breath and walk away, end the training session until you are calm enough to begin. you must learn patience.
exercise question, when you say you walk your dog how do you walk, and for how long, and how often?
When you are walking a dog to tire her out (a tired dog is a happy dog!) the walk should be at a brisk pace for her. If you are walking her fast enough she should be focused on the walk not worried about sniffing the ground.
Sniffing the ground should be a reward and not done without your permission.
How I trained leave it was... you start with a peice of food say a cherrio (something that is not a high value food reward) you hold it in your hand and show it to her, as soon as she goes for it say leave it and close your hand. When she looks away from it (might take a little bit since she will try to eat your hand at first) you give her a different treat (not the one you want her to leave) something that is a little more valuble like cheese. Once she starts to leave it consistantly then start working on setting it on the floor, once again if she goes for it cover it with your hand. once you can do that graduate to having it on the floor and walking by it (with her on leash) Once you can do this with a low value food start all over again from the beginning with a higher value food. Keep doing this until you can eventually leave your dinner on the floor and she will leave it when told.
Rember you can do this training while you are watching tv.
Having fun yet

because now you have to apply what she learned in the house to her walks!!
It will take Time, Consistancy, and Patience, but in the end it is worth it for the love they show us in return.
oh forgot to add if you are not doing this already I would teach her to sit and wait before she gets her food. To do this tell her sit start to put the food on the floor if she gets up pick the dish back up tell her no and sit. After what seems to be the 1,000 time

she should stay sitting while you put the food down. Tell her ok before she starts eating. Eventually you can have her wait for longer periods of time before you tell her she can eat.