My dog is aggressive and barks at other dogs after a traumatic bite.

Poor Panda! Unfortunately she had a very traumatizing event during a very crucial period of socialization in her life. I would not consider her a waste of money. She could be fearful reactive (I have one of these) that acts so aggressive to try to scare everyone away because she is scared to death. I don't like training at dog parks. The dogs are not controlled and it is likely to end up with her having another bad experience. Not everyone understands dog to dog behavior, so there can be fights at dog parks. I would NOT recommend a shock collar. Her response is most likely fear, and we should not punish fear. Imagine if you fell off a roller coaster (major injuries but survived) when you were a young child, would you want to ride a roller coaster again? I am sorry that you have not have luck with trainers. First, you might need to reconsider what you want Panda to do. Do you want her to go for walks where she might see another dog? Or are you wanting a dog to go to dog parks and play dates etc? I think that with a good positive reinforcement trainer coupled with a veterinarian who might prescribe a medication to ease her anxiety that you can successfully train Panda to go for walks etc. I think that we just need to help reduce her fear and create positive situations for her. It will take time and you will need to be patient with her. Thanks for reaching out to Petco Pet Education Center, formerly Petcoach!