WFFF is a good place to start. Also, there's immense amount of delta gouges on the web, or just ask your buddy, and they'll point you to hours of extra studying for the same subject, over and over again. To be honest, it was much less math oriented than before, but more new subjects that are covered than the canned "old" gouge. So i think it's a more comprehensive test, but not harder necessarily.
If you pass your ATP written, and you have a broad working knowledge of various systems of a jet transport a/c works, you should do just fine. Spend more time prepping for your panel interview, if you think you have too much free time.