Have your tried the Ai fluid in the spinclean?
You need to do a side/side comparison. That is hard to do, can you manually clean one side with X and the other side with Y then listen?
With your Degritter after, not sure the pre-clean is as important. Do you use anything in your Degritter? that also make a huge difference.
I would just do what is most convenient for you. My cleaning is also a 2-3 step process, with a manual clean before UC. If it's really dirty, will do both steps twice.