There's not a single method that you should use. Many people use very different techniques for their horn nocks, all with excellent results.
Here's the process I use myself. I floortiller the stave first. When floortiller looks about good, I fit the horn nocks. When the nocks are applied, I can go to long string tillering or even to short string tillering straight away. But I don't cut temporary nocks in the bow at all. You need to fit the horn nocks any way, so why create temporary nocks at all?