I'm not sure I understand the question. The first part of your post talks about grouping bareshafts with fletched arrows and then you ask about how to aim. My first thought is that you have to learn to aim first before you can worry about whether or not everything groups together. In other words, if you have them grouping now, then you must be using some sort of aiming method and it is working or you are just getting lucky.
My recommendation for aiming would be to read some of the posts in the Shooters Forum on that subject and then try one or two of them out. Most prevalent is probably instinctive followed by gap. Once you have the aiming and form all sorted out, then you can worry about grouping. If your form is out of whack and you don't have a consistent aiming method then your arrow groupings won't really tell you much.