I'm also an "Eyeballer" of course it's kinda difficult when your crosseyed and your eyes are too close together....
I also shoot with 2 fingers under cause I'm missing my third and fourth fingers........Naw I'm just kidding. I've got all my digits and my eyes are fine.
Hope I didn't offend anybody? I was making fun of myself. :rolleyes:
Seriously, I have never used a bow square. I can get it close enough by just using the arrow nocked onto the string and eyeballing it 90deg. or level. Then I lightly crimp a brass nock on the string and go from there.
One thing that will help and I use them all the time on every one of my bows is illiminator buttons. The little rubber deals that you thread onto your string and I usually keep 3 or 4 below my nock point on my string so when one of them breaks I just slide another one up. I use one as a cushion under my arrow nock so I don't pinch the nock when I draw.
I have also found that you can actually slide 2 or 3 or 4 illiminator buttons up under the arrow nock and use them as guides for string walking longer yardages, it works well but I'm not a master of it. It's just something I've been playing around with. It allows you to point the arrow tip directly at the target at all different yardages depending on where my fingers are on the string.
Just remember to make small adjustment when tuning a bow becuase sometimes it only takes a 1/16 or 1/8 inch to make a big difference in arrow flight.
Good Luck!