Lots of great info here...
I bare shaft tune. Always! I start by getting nock height established, then begin with spine. However, if your spine is WAY off, your nock high/low will show falsely sometimes. Or if your nock is set too high/low it too will show a false reading. If your spine is good then you probably do have a form or your gripping the string wrong.
I switched to a tab last year and all I can say is wow! What a difference it made in my shooting. Now I wil say, i had to dedicate to switching to the tab. It was not easy. But after a week of blind bale and the tab breaking in (I highly recommend Rick Barber tabs) it was like magic!
Now back to bare shaft. I highly recommend starting with one bare shaft at 10y. Get it cut close to where you are showing lightly weak. Nock left if your right handed. Then cut and fletch another arrow. Go out to 15y. See what happens. Then 20. Then establish your point on(if you want) and tune there.
You want the 2 arrows to impact at the same spot. I typically do not worry if I still get nock left with the bare shaft. As long as the arrows impact at the same spot, I am happy!
I typically stop at my point on. I don’t tune past my point on. Typically that is 25-35 yards.
Now, here is my biggest suggestion, ONLY shoot those 2 arrrows for a week. Make sure you are happy. Then cut and fletch the rest.
Bottom line, bare shaft is MY preferred method. But you need pretty good consistent form to do it. Hence, why I suggest not rushing and shooting the 2 arrows for a week. Heck, we all have good and bad days shooting.!
Hope this helped.