I consider the chapters in Les's and Chris's books the definitive tomes on the process. I have both books and they are my consistent references. But, quite frankly, the split grade process is so simple that you just need to do it. You will gain experience with your equipment, chemicals and process.

I personally find split grade printing using RH Designs wonderful f-stop timers the most artistically intuitive printing process that I have practiced in nearly 40 years. Visualization and realization without the technical fog. I no longer worry about grades, filters, brand differences or lot changes with my papers.