This isn't really directed at you, but I'm really astounded by the number of questions there are about "neck reining" a horse and trying to teach one to "neck rein." It's something that is so simple, it's really just riding your horse.
How exactly are you cueing this horse? Western horses (show horses, I mean) aren't really "taught neck reining," it's just more of what they've been doing since they were young -- ridden off of legs and seat. When they are young and still two handed, either in a snaffle or a curb, you're never just pulling their face around to turn, there is always a push from the outside with both the rein and mostly from the seat and legs.
If you are currently plow-reining to guide your horse, then you need to first start riding more through your seat and legs, which means your legs are always in contact with your horse (from thigh to foot).
Obviously when you are first starting a horse it takes a more obvious cue, but the more familiar they get, the less you have to do.
This is the level of control you should be striving for. Notice that she is using her seat and legs to maneuver him through the pattern:
As always, I recommend finding a trainer that can teach you and your horse. Especially in lead changes which are practically impossible to teach through the written word.