How do I get my dog to behave around other dogs?

My dog is a nightmare with other dogs when walking, we don't take him off his lead as he would be uncontrollable, he shakes when he sees them then barks and lunges for them when they get close. Occasionally he's ok for a few seconds but then he'll start to growl.

He's been like this since he was attacked by a staff as a pup (he's 2 now). He's fine with my sisters dog after many hours of getting him used to her but she lives on the other side of the country and none of my friends have dogs I can train him with.

What is a VPN?

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