There's a document... Do a Google search for the "Instrument Know All" handout. There are a couple things on it that are different for helicopters, but it's a good product start with to brush up/warm up your knowledge. Also, I don't know your situation, but it's possible to do it concurrently with your company's initial or recurrent ride, give it some thought. You know (or should know) the aircraft fairly well, and it's no cost to you. Good luck, man.
