That's pretty much what I do. I have a 3 gallon VP race can which is like the perfect size. I take that to gas station. Put in 3-3.5 E85, then 7 gallons or whatever it takes to top it off for E30-E35ish. My E station is like 100 miles away, but we go there every so often for shopping...
I would recommend reaching out and contacting any you are interested in first... I'm sure you have some questions etc. How quickly they respond/how they respond may help you decide what route to take.
The fact is most/if not all good tuners tend to get overwhelmed after they start doing good...