1) DAV- listen to them as they will be you best advocate.
2) I know it costs money, but go see a specialist. VA cannot refute the advise of a specialist with the advise of their "primary care" idiots.
3) be patient- expect VA to fight to refuse every penny. It may take a year or two to get a decision. Good thing is your payment will be retroactive to when you filed the claim.
4) document everything- non-measureable things such as how this disability affects your day to day life and impairs your ability to earn a living will help tremendously. Search the VA rulings for the outcome of similar conditions and use those to support your claim