Hi Ashley! Well, leash-training a full-grown Mastiff is going to be a chore, no matter what method you use. As for the tug toy/food problem...if he's more rewarded by toys, let him be rewarded by toys. That's fine. =) My Border Collie is a million times more toy motivated than food motivated, and performs sooo much better when rewarded with a good game of fetch. I'm not sure the leash-training method I use most often would do much for your big guy, because...well, he's a Mastiff. Lol! But you are certainly welcome to try it.
As soon as his shoulder gets even just a little past your knee, spin around and walk the other direction, and keep doing so until you have mastered a loose-leash walk. This could take a matter of minutes, or a matter of a few weeks. Being such a large dog...it may not make a difference at all, because the idea is that they correct themselves both with the leash and by losing your companionship(because you "abandon" them by walking the other way). You can try this, but I'm not sure that your Mastiff would really be "correcting" himself, because he's a huge dog, and unless you're a body builder...well you may just wear yourself out, and you may not be able to even spin around and get him back to you. He may be completely physically capable of dragging you right back his way.
Another thing you can work on is coming to your left side on cue. DTA has a lesson on this, and calls it "get in." I prefer to use "on my left," which means to come to my left side, sit, and look at me, facing the direction we are about to go. Teach him this, and holding either a toy or food, take one step forward, asking for a sit as soon as you stop. If he rushes ahead, say, "Ah-ah!" and lure him back in the "get in" position, or spin around. Since you have the oh-so-wonderful toy/food, he'll be enticed to come back to you to get it. Reward him when he returns to you. Repeat this several times, and slowly add more steps when he is ready. You can do this off leash in your home or yard. When he has mastered at least several steps at home off-leash(or on leash, whichever you choose to do), then incorporate these same techniques in your walk. You might look into getting a dog backpack and putting some weight in it(water bottles, whatever) to both tire him faster and make him feel as though he has a job. If these techniques do not work, feel free to send me a PM and I will give you any advice I have. =) Good luck to you!
