As he begins to venture off further and longer during walks, you will want to instill cooperation and a "checkback" in him. In his NA Test, he will be scored on Cooperation, which is how well he sticks with the hunting party as they move about the field. Frequently change directions on him (saying nothing), so he learns to pay attention to where you are so he doesn't get left behind. To train a checkback, every few minutes on a schedule, call him to you and reward him with a treat or praise (alternate so he doesn't know which he'll get). This will get him systematically checking in with you, which is necessary when hunting in heavy cover.