Honestly, you want it waterproof? Contact the best patent attorney you can find and let them do it. There is no way you will not make many mistakes without having years of practice and learning. Just browse some questions or the internet to find out just how many mistakes can be amde in a patent that later invalidate it.
Actually, let me add an example:
Let's say I tell you, that you may sue me for some million dollars based on a document you may now design yourself, but if you step into any legal trap while designing that document, you will lose. Would you do it yourself? Or would you hire somebody who's job it is to know those traps?
Because that's what you want if you say water-tight. You want it to potentially win a multi-million-dollar lawsuit. And if you do it yourself, it won't. It just won't hold the moment it becomes important. If it doesn't, whatever, it might last 20 years without anyone caring. But the moment it might earn you money ... yours won't last. An attorneys might.