I guess what I don't understand about things like CI is, why "summarize" the curve with a straight line of best fit when you already have the full curve?? Why not simply plot the curves and compare them?
I don't want to give the impression it is wrong to use CI. I would say that with most of today's films which have relatively long straight line sections, CI is fine as long as the exposure range lies on that straight line. However when dealing with high contrast situations and/or minus development, I need to know what the ends of the curve look like - particularly the shoulder. CI on it's own doesn't tell me enough, and it complicates things for me.
If you've got an understanding of how flare impacts both testing and real world photography (thanks to Stephen and Bill), the rest of the testing for your personal EI and development times should be pretty straight forward. Don't overcomplicate it. And take it from someone who's been down all these roads - don't waste too much time on the n'th degree of precision. There are people out there who rate their film speeds in 1/4 stops, try to get to within 1 density unit of their targeted Zone VIII densities, and determine development times in 10 second increments. I don't care who you are, there is no such precision in the process. Strive for high quality and consistency, but dont get sidetracked into endless testing.