I’m using a fuel-it test kit.
https://fuel-it.com/products/ethanol-content-tester-vial-only
It is really compact but I ordered the vial only by accident when I was ordering my eth sensor. I got a syringe with aquarium tubing off eBay since I didn’t have the pipette. Get a vial that is small and etched numbers vs a plastic cover with the numbers.
For the spreadsheet, it is designed for E85 summer/mid/winter blends with winter being lowest E content (not necessarily flex-fuel but my tests have never shown less than e70).
The 51% min for flex has always thrown me a bit as the pumps here list it as 94 octane but that would have to be mixed with absolute crap and as I said above, I have never tested lower than 70 on the pumps I go to. ymmv.
This gives a quick definition for class 1,2,3 e85 but if it is a flex-fuel pump, manually test it to be on the safe side.
https://www.autoblog.com/2007/02/27/when-is-e85-not-85-percent-ethanol-when-its-e70-with-an-e85-st/