Tergikleen or AIVS formula 15?

Interesting. I'm not sure what purpose having an old and new brush serves, other than needing to buy brushes less often. 
I also give them new sleeves and a sticker with the date & fluids used. It's the Engineer in my bleeding over to civilian life 
I used to use a method similar to yours with the Spin Clean and Disk Dr. It's not bad for the money invested, but now I prefer not to have the record touching the lips of a vacuum machine after it's clean. Possibility of recontamination bothers me. 

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. 

I would but formula 15 is not a concentrate. It would take the entire bottle plus some. 

In the Degritter I've tried the new version of the fluid that ships with it, but the AI concentrate that's made for US cleaners works better. After that, I have a second tank for the rinse with just distilled water.

ENZYMATIC RECORD CLEANING CONCENTRATE FOR ULTRASONIC RECORD CLEANING MACHINES

I used and liked AI products for years. Deep cleaned some records recently using Walker enzymes, then Pro-Ject vcm, then a rinse, then into a Degritter II, then a final rinse on a Project. Noticeably quieter surface noise.

Slaw,

What fluid do you have in the degritter? 

I have the second tank so I can use the rinse feature. You might want to get one for your final rinse, it's very convenient. 

Got a link for Walker?