Wallaby - Yes, that was me (and her). I am getting so much conflicting information! I've heard using shanks is a must for neck reining and now that I should not use shanks. ???
To teach neck reining, you want to have her in a snaffle (ie, no shanks). You don't want shanks to teach neck reining because in the process of teaching, you're probably going to need to direct rein her quite a bit while giving the neck reining cues and you don't want to direct rein in a shanked bit.
However, once she's consistently neck reining 85-90% of the time, you can move her up to a shanked bit.
But, you never really need to put her in a shanked bit to neck rein, no matter what you may have heard. I taught my mare to neck rein in a snaffle, now we actually ride bitless and she neck reins just fine.
If you're showing western, and she's over 5 or 6, you will probably need to her to be in a shanked bit and neck reining, but other than that, there really isn't any pressing need for the average horse to be in a shanked bit.
The thing with shanked bits and neck reining is that when you're neck reining, you have loose reins and you never actually contact the horse's mouth, you just move the reins. Therefore, to feel the tiniest moves in the reins, a shanked bit can be helpful because it magnifies everything you do to the reins, times the length of the shank, inside the horse's mouth. Neck reining in a snaffle is a little different since even though you're still just moving the reins quietly, the horse is responding more to the reins on her neck than to pressure in her mouth from the bit.
So, some people who have "deader" horses might benefit from having a shanked bit since their horse needs a little more oomph to tell him/her to stop or what have you (which is a different issue all together since I'm a believer in training for the horse you want and taking the time to teach those "deader" horses to be sensitive, but whatevs) but the majority of horses will do fine neck reining in a snaffle.
Basically (maybe this will make it easier to understand, I totally understand how confusing it is!) neckreining=/=shanked bits, but shanked bits=neckreining. Snaffles (no shanks)=direct + neck reining.
Does that make sense? Hopefully someone who can explain it better will come along. :)