I have a snaffle bit in my in my homemade breaking head stall but I don't have the reins attatched to it. I just have it there to get the colt used to something in his mouth. I start off letting the colt wear this head stall for a couple of days dragging the reins. This teaches it to "Stop" and back up to get off the reins. When you see him doing this on his own then it is time for the ground work to begin. Most colts have plenty of "Go" so first you need to learn to "Stop". When he starts bucking and you pull back on the reins, it will hopefully stop, if not just gigem up and make him buck harder and harder till he finally get to tired.
Hopefully you are still in the saddle.
Now it is different for everyone. I have cow horses, so the faster I get there head down and stop to see what is in frount of them the faster they read the cow and then the turning comes natural.