A German friend of mine swears by working them hungry and putting the food along the artificial training trail - not at the end. He puts the food in 4 or 5 points along the trail. His view is that the dog is rewarded 'along' the track and will not rush to the end to get the reward. The trail is the prize - not just the end of the trail. He is the most successful dachshund trialler and trainer in Germany and, probably Europe so he is worth listening to.