Dog aggressive with particular dogs

Hi, I know this is a well covered subject but I really need help with my dog so he can live a happier life. Dan is 4 1/2 years old and a rescued crossbreed (possibly Dobermann/Rottie/sighthoud + other!). We adopted him at 18 months old and have no history on him. He was petrified of men when we first got him and he would bark and growl and lunge at any man he saw. This is now under control and he will now walk past 99% of men with no reaction. Unfortunately the method I used for this hasn't worked on his aggression towards some other dogs, mainly bull breeds and their crosses, mastiff types, golden retrievers and GSDs. He also dislikes uncastrated males. He's fine if they ignore him, but if they come towards him, he will growl, then show teeth and then bark and snap. He's twice as bad on lead. He will also do this over treats etc. He's fine with certain dogs, even playful, but they are few and far between. I'd love him to be able to relax around other dogs and there's always the worry that the other dog will go for him as has happened twice already. I also worry that he will bite one day although it is all noise now. Obviously people avoid us at the park, but there are a lot of dogs who run up to him and then get a gobfull from him.
I have been really trying to train his "leave" in regard to this and he's doing quite well in some situations, but once he starts, as happened twice today, I can't get through to him. The dogs he reacted to didn't do anything unreasonable to "provoke" him. The GSD ran up to him face first and the chocolate lab sniffed my other dog. I am sure it's fear based as he will go out of his way to avoid other dogs most of the time.
Please help as he's such a lovely dog when he's relaxed.
Jo

what type of lead and how do you hold it?

It's just an ordinary lead, not a flexi, and I always try and keep it loose.

Do you have any friends with sociable dogs that you can walk with? Sometimes dogs learn from other dogs as well. At the very least it would socialise him with one other dog. I`d say persevere - you seem to have done really well so far. It does take a long time to `unlearn` bad habits.

We've had him for 3 years now. He's fine at agility with the other dogs as they don't bother him, although one dog there, an entire male, very dominant, causes him to bark non-stop... At the park he socialises with lots of other dogs. When I say socialise, he hangs about the edge of the group of dogs and avoids them if they come toi say hello. Most of them know not to bother him now, but a few still try. If they come towards him, he freezes first and then does anything he can to get them away from him. I think that he is the result of under-socialisation when he was a pup personally but I just can't seem to get him past this. I give him lots of praise and treats when he doesn't react to another dog, but the dog will inevitably come over to try and get the food too, causing him to tell them off, undoing what I've just done.

Sounds like you have done a lot of great work with him so far
And in some respects he is kinda right that if he dosent want another dog to come up and he cant get away cos he is on the lead, that dog comes right up in his face then he is correct to tell it off (although that is not what you want)

With my boy who was guarding me (not really agressivly but I wasnt happy with it - he would push between me and the other dog and shove them away) I would put him in a sit stay with really good treats in my hand then I would reach a little towards the other dog and reward my dog (other dog was on the other side of me) then when he was chilled I would touch the other dog and reward my dog at the same time
gradualy hold back the reward till after I had patted the other dog
then worked on treating the other dog then treating Ben
taking baby steps each time

On the lead meeting other dogs I wouldnt force him, if he looks even slightly not happy about an approaching dog turn and walk away - hopefully that will also teach him off lead when he dosent like a dog to just move away

At the park yesterday, a dog came hurtling towards him and my other dog intercepted it (she'e very sociable!) and I called him away which I admit I wouldn't have been able to do a few months ago. I have been working on recall quite a lot and it has worked a couple of times now. I usually try to let him off lead as much as possible so he doesn't get too much into the habit of aggression if that makes sense and call him to me if I see a dog I don't think he'll like. Unfortunately he's a bit unpredictable and sometimes goes for dogs I thought he'd be ok with. He also seems to "protect" Myrtle too (who definitely doesn't need it!). I was wondering if I could try to make her top dog, taking the pressure off him to protect her, but other than feeding her first, I don't know how to go about this. Also she's only 11 months old and I don't know if she's a bit young for this?
Jo

Sorry, but YOU can't decide who's top dog in your pack... Regarding feeding, I'd just fill up their bowls, and set them down at the same time... Eventually the dogs will work it out... You also can't speculate on what kind of dogs your dogs do or don't like. Many times they just don't agree with you!

Lene is correct, you can't and shouldn't interfere with any ranking your dogs may have within their group. It will only lead to confusion and frustration for your dogs.

We have 3 bitches and they all have different roles, depending on the circumstances, and they have all just developed into those roles without us meddling with it.

[QUOTE][You also can't speculate on what kind of dogs your dogs do or don't like/QUOTE]

He has not met one GSD that he has not reacted to like this in the 3 yrs I have had him. The same can be said for Staffies. His reaction to these types of dogs is far more severe than others. He has been attacked 3 times by Staffies in 3 years so I believe this has caused his fear of them, although I tried my best to handle the attacks in a way that wouldn't make him more fearful. He is a generally nervous dog which is why I think it is fear based.
As I say, he is fine when left alone, he doesn't approach another dog to have a go, it's only the many dogs at the local park off lead who run up to him head on, no-one bothers to call them back, just let them run up to other dogs willy nilly and then give me abuse for having a "vicious/aggressive dog". He is ok with them sniffing his bum for a few seconds, but any longer and he turns around and growls. His first reaction in these situations is always to freeze.