Rott needs harness--how to train??

[lotsarotts]

I work with a local rescue group and have recently adopted a male rottweiler who is around 3 years old. He was recently neutered and has been diagnosed with a herniated cervical disc. He is mellow and has a sweet personality, and has been good with people, dogs and kids. This guy was found on the street. He seems to have had some training because he does respond to some verbal commands. I have 3 other dogs--10y rott mix male, a 6 yr rott female, and a 1yr rott female, all S/N. All dogs have been getting along well. My 6 yr old female is very dominant but very trained.

Although this new guy is NOT food aggressive in any respect, he is possessive of some toys. If one of the dogs approach him or get too near the toy he is playing with, he will growl and bark at them to keep away. If he does this to my dominant female, she won't always back off!! I will verbally show my disapproval (and the female will come to me)and I will ignore him and leave him alone. This usually works but was wondering if there are any other things I should try. A problem is that I am not allowed to correct him with any training collar---he is only allowed to use a harness. I have used treats to coax him away from the toy but at times he becomes very focused on the item and this doesn't always work. He is a fairly sensitive dog. By this I mean that when I ignore him and express disapproval verbally, he reacts by following me around and trying to get me to pet him. Thanks for any help you can suggest!!

[lad]

Here are a couple of things that I thought of.

1. A Gentle Leader Head Collar. It requires very little force to control your dog. It basically control the direction that he points his head. If this is still not safe, given his condition, have you considered:

2. An electronic training collar. I use one to control my boy off lead, and have been very happy with it. It provides a shock from a 9V battery. I use a PST-2M. It is a little pricey but it works very well, is waterproof and has an advertised range of 2 miles!

[lotsarotts]

I will ask the vet about using the gentle leader. I had used an electronic training collar on my oldest dog but after he was already trained, for off leash work. It worked well but I was afraid without much training and not knowing this guy's history it might freak him out. Did you use the collar to train your dog??
Also, what should I do when this guy is just getting dominant or possessive??