Ok, my embarassing moment when I was 19 yrs old..... I was riding with a very successful reining trainer who had just moved to our area. I had the horse I'd always dreamed of, though some of our issues weren't included in my dreams. I worked with this trainer for a week straight, hauling my 5 yr old gelding out to his place every day, taking full advantage of his "new to the area" promotional offer with a few of my friends. One night, we ran into the trainer at a night club after he had a few too many to drink. Now, almost 10 yrs later, what he said in his drunken stuper goes through my mind every day with every horse that I work. He said "how long have you had that paint horse?" I replied "about 2 yrs". He slurred back "yeah, I figured, definitely long enough for the horse to start acting like his owner, you both take things too seriously, try so hard for perfection that you can't get it right. You need to relax and have some fun." I was left speechless. I mean, how dare he say that my horses problems were my problems. After my initial shock, I thought it through and realized that he was right. My horse was a 4 legged version of me. His strong points were my strong points, and his weaknesses were my weaknesses. If that's not a slap in the face...... Everything that bothered me about my horse were the same things that bothered me about myself. Ever since then, whenever I work with a problem horse (coincidently now my profession) I try to use myself as an example, letting the horse do what he does well, and giving him strength in his weaker areas.
Sounds crazy, I know, but I couldn't help but notice how your horse was labeled, and how, in my experience, horses live up to what they are labeled as. Horses that are difficult will always be difficult, where as horses that are misunderstood or simply confused have a great chance of stepping out of their difficult state once they have someone who is communicating. I find it no coincidence that the rider who looks for things to worry about has a horse that is always spooking. Nor do I find it a coincidence that the rider that can't seem to find the right fit has a horse that is showing signs of discomfort.
As far as your questions go..... I could care less if I am carrying a whip, crop, bull whip, or nothing at all. However, if my horse is showing signs of discomfort with any of those things, you can bet that we will be working to overcome them rather than avoid them. Here, we are looking at issues of adaptability and trust. My horses learn that if I am holding it, then it is obviously not something to be fearful of.
You are looking at the symptoms rather than the cause. It isn't the slack in the line that is the problem, but the horse on the other end of it that is confused about the contact. That is what needs to be focused on.
As long as you are having problems with trainers, your horse will have problems with trainers as well. Based on what I read, I am not in the least bit surprised that you are having trouble teaching new things, as there are some pretty big gaps in your foundation. Good riders and trainers have a goal, but they do not have an agenda. As long as you label your horse as something special, he will behave like something special, and not necessarily in a good way.
Good luck, you are young and dedicated and you will get it figured out little by little. Remember, you are hiring a trainer because you are putting faith in the fact that they know something that you don't. However, if you are stuck to what you already know, then it can be very hard for you to change, and very hard for your horse to change.