I think that's good advice. The review books are designed to help you review the fundamentals (math formulas, grammar rules), but not to teach you how to do the math. They teach you how to apply your math and verbal skills to a weird test like the GMAT, and some are very good at that (Princeton Review in particular. The OG doesn't have any tips but the practice questions are awesome.).
If you're really rusty on math and verbal skills, it would honestly be worth your time to take a math course and an English course at a local community college near you. When you start out with a 350, it's more likely a problem with the fundamentals and not the GMAT itself.
Good luck! I hope this helps!