Have you desensitized the horse to lead rope first, and are you able to throw the lead rope all over his back, legs, neck, and around his head. If not then go back and get him quiet when you throw the lead rope on and around him. Then move onto the stick and string the horse should not fear you or your tools, and your tools are extensions of your arms. Start with rubbing the horse all over with the stick, find a starting point I usually aim for the shoulder area, rub the air around the horse when he stops moving retreat. Then do it again until your able to touch and rub him all over with the stick. Once you can touch him all over with the stick then use the string, CA calls it flogging with kindness if you can fling the lead rope all over him then gently throwing the string across his back, around his legs and neck should not be a big deal. The last thing you do is slapping the ground with the string and again you have to find a starting point start out low energy and increase as the horse gets more comfortable. With all of these exercises most horses will run in circles the first time you fling the rope, or rub them with the stick, especially slapping the ground with the string, the key is to keep doing what your doing with rhythm, until the horse stops. When he goes like he is longing keep bumping his head to you so you have two eyes and move with him and stay at a 45 degree angle so he cannot run you over, and keep your lead rope up so you can push him away if does get to close. He will run in circles, back up, move sideways, try to go forward while looking for the right answer. You have to keep going until his feet stop moving, and he shows a sign of relaxation, drops heads, licks lips, cocks a hind leg, stands for 15 seconds, blinks his eyes. Horses learn from the release of pressure so if you stop while he running around then he is learning that is what you want. Also make sure to check your body language make sure your relaxed and low energy. You need to find a starting point for all the exercises. The desensitizing is also best done after the horse has done some work and wanting to stand and air up.
I follow CA method and have done these exercises with every horse I have and that I work with. The thing to keep in mind is don't quit to soon, the horse will find the right answer you have to let him. Some horses are more sensitive then others and it takes a little longer for them to find the right answer but they get it eventually, usually in under 5 minutes. Every horse I have will ground tie while I walk around them popping a bull whip and they all started running in circles while I was slapping the ground with the string.