I think probably we can get her started in the right direction here and now, free of charge! No need for a trainer right yet, though it is helpful (as long as they're worth a damn). From what I've read, and what this sounds like, I'm going to go with a fear aggressive/reactivity that needs to be addressed with a desensitizing routine. Which if you do a search on the forums for Desensitize, it will come up with all kinds of things.
Your dog food treats are not high enough in value to get his attention, start using cooked chicken or low fat string cheese, or something like that. It will grab his attention more then dog food.
The basic premise of a desensitizing routine is to work your dog outside of his reactivity zone, and for him to maintain focus on you, not the dog off in the distance. (Yes, you need a dog he doesn't know for this) This is total positive reinforcement with NO corrections, if he reacts in a negative manner, then he gets taken further away from the other dog, and restart at square one.
The objective here is to get him closer, and closer over many repeated sessions to a strange dog without any reactivity. Until finally, he can sit next to another dog and be INDIFFERENT, your not looking for happy, your not looking for playtime. Indifference is what your looking for. From that point on, and for quite a long time he should be rewarded for every positive encounter he has with another strange dog, even if he just walks by them without a peep.
Now in order to help you with this, you need to brush up on your marker training skills. I HIGHLY suggest the marker training dvd here at Leerburg, but since things are tight in the pocketbook, then I do believe there are a few free videos with an intro to what marker training is. I don't know how your youtube video did it, but there's a right way and a wrong way. The Leerburg way is the right way. I will also suggest that you familiarize yourself with the Pack structure training dvd to become a more effective leader. There's also LOTS of free information right here about pack structure, you need only search , or ask!
Last but not least, we go to the NILIF program. ( Nothing In Life Is Free ) He must perform an obedience command, or other command before he is allowed to get what he wants. Toys, food, out the door, up on furniture (if you allow it), to be petted, anything. He must learn to be patient, and good house manners. This will also reinforce your status as a leader, and give him more confidence in you. This can be enacted today, at this very minute, and from here on out for the rest of his life. Be consistent, be fair, and be his leader. He doesn't need friends, he needs you to lead him.
Cassy & Leo enjoying a nap.
