I tie nail knots, not needle-knail knots, but since the premise is the same, I will share what I have found:
I don't like the tie fast tool but some manufacturers make a set of nippers with a small nail knot tool that I find works very well. It only works if you remember to keep tension on the leader end of the mono, pressed onto the tool with your thumb (left hand) and pull the tag end slowly with a pair of pliers (right hand) to constrict the knot and pull it off of the tool and onto the fly line.
If you do this the wraps will always come out in a perfect barrell before you cinch it down all the way. It works even with 45# hard mono. You can make sure all wraps are aligned and move the fly line around inside the barrel until perfect and then tighten it up with the leader end wrapped around your palm (LH) and a pair of pliers on the tag (RH).
I struggled with it as well until a friend showed me to keep the leader tight between the tool and your thumb. Then a light went on.
Hope this helps.