Question: I just purchased a 15 year old TWH mare.  The previous owner rode her bareback with a stainless, jointed-mouth, curb with approx. 6" shanks.  Very severe IMO.  She constantly played with the bit, even chomping on it with her teeth.

When I brought her home, I tried her in a copper, jointed-mouth curb with 4" shanks.  Still severe IMO, but I wanted to find out if she liked the copper better.  Still chomped and played constantly, although she responded very lightly to the bit, which I liked.

Last night I tried her in a stainless, solid mouth, low port curb.  She seemed to relax a lot better with that, and didn't play with it as much, but I didn't have very good control over 
her as far as turning left or right.  She doesn't neck rein, so trying to direct rein with a solid mouth curb is difficult to say the least!

Question 1:  What kind of bit would you suggest for her?  I don't like the broken mouthed curb bits, but is this what I'm limited to with her to be able to have lateral control?  I'm also showing western, so need a western style bit.

Question 2:  How would you teach a 15 yo to neck rein?  I want to show her western, so this is a necessity.  How long will it take?  She is very smart, willing and responsive and I'm just as pleased as punch with this purchase!
Thanks.

I think she has answered your first question for you -- go with the solid mouthed, low port curb which she seems to prefer. The other type of bit (broken mouthpiece curb) is actually more severe and not comfortable for some horses.  Find a well made short shanked low port curb that fits her, adjust the curb strap/chain so that it touches her jaw when you have the shanks pulled back at about 35 degrees from vertical, and (this is important) ride her into lateral moves with your legs, don't pull her into them with the reins.

How?  the answer to that is the same as the answer to your second question. Start out with one rein in each hand, English style.  (yes, even  in the solid mouth curb).  Ask her to turn to the right by moving your right hand out to the side, "leading" her into the turn with the right (direct) rein, while laying (not pulling, just bringing your left hand across the withers and letting the rein drape across her neck) the left rein (indirect) against her neck just in front of the withers.  At the same time, shift your weight a little to your right buttock (don't lean over, just subtly shift your weight that direction) and press with your *left* leg against her side at the girth to ask her to turn toward the right.  As soon as she starts the
turn, discontinue any pressure on the right rein, and let the legs, weight and indirect rein cue continue as she turns.  If she stops turning, reinstate the direct rein cue for a second, then again discontinue it. 

Practice this in both directions, obviously with the opposite cues for a turn to the left. Over time, reduce the action of the direct rein, and rely more on your legs, weight and the indirect rein for a turn. BE sure not to pull the indirect (neck) rein over the neck, or pull back on it as you ask for the turn, just continue to lay it against the neck, so that the horse
looks in the direction of the turn and does not cock her head in the opposite direction in response to a tight rein.  Start with large, wide curves, then smaller circles and figure 8's.   After she has learned to do these things well while you have one rein in each hand, change
over to one handed riding.  Voila, neck reining!

A horse can respond adequately to lateral aids for a turn in a solid mouth bit, as long as the weight and leg aids are also used -- there is nothing magic about the broken mouthpiece for developing the ability to turn on command.  Just be sure you don't pull a steady strong pull to ask for the turn -- vibrate the reins in little pull/slack motions and leave the rein
slack when the horse is turning. 

It sounds as if you have a really nice horse ... enjoy her!

Lee Ziegler