Slasher, without concious thought of "how far", just get a very small spot to focus on. Practice
good form, concentrate, draw, anchor, release, and follow through. Repeat at close range until they are all landing where you want, then begin moving back. When the group starts to spread, step closer, and do it all again. As the distance increases, it becomes more difficult to focus on a TINY spot simply because it becomes more difficult to see. This is one of the challenges to true instinctive shooting.
If you can train yourself to focus on a speck, with practice you can hit it.
The only problem I encountered was that when shooting from a tree stand, the target looked farther away than it really was. I shot high often. I really had to work on that.
Good luck.