I know that it has been said before, but you really have to question whether you need to be in stealth mode at all. If a product is really that revolutionary no one will get it anyways and you will have to beat people over the head to come along for the ride even if it is out in open. Look a Tesla an accomplished scientist in the field of energy and his quest to push alternating current. It was far superior and even so, and even though he had proven himself time and time again Edison still had no interest in it. There are very few companies that are in stealth mode that should be in it. It just makes everything and I mean everything harder to accomplish. If the idea is that esily stolen then it will just be replicated after the fact by well funded entities. One only needs to look at Groupon as an example, no one was interested in the market until Groupon proved it out and then given the simplicity of their idea everyone and their uncle replicated it. If the only competitive advantage is that you will hit the market first, then it little advantage at all.
That being said, to attract top talent to a stealth operation you will need a name. You are going to have to focus on recruiting someone with a stellar reputation so that others will follow. Expect to reward that person handsomely for putting their reputation on the line. Other than that, you are going to have to tell people what you are working on, or pay them well over market rate. Those are your options while in stealth mode.