Sadie is learning how to heel. She does ok, but she's having trouble learning to turn right, but does ok when we're turning left! She can also heel if I'm a couple feet in front of her, and I tell her to heel, and then slap my left thingh. But if I stand in back of her, she just goes and sits in front of me! Is there a special training collar that would help? What is the best training collar to use when training a dog? Thank you!!!!