frankly I wouldn't bother with the clay. I got one and did the 300zx the other week, took a lot of time and effort. Was super smooth and lovely after, but just 1 week later it was back to exactly how it was before. A waste of time if you ask me.
You obviously dont know what you are doing then. I am a rank amatuer at this detailing lark but even I've found how brilliant claying can be. My paintwork is always smooth as a result of a twice yearly clay and decent washing.