One of my trainers has told me that when you start using more advanced releases, first grab your horse's mane and give a little more than you think you should. This will keep you from accidentally pulling on your horse's mouth over the jump. It will also teach your hands to follow the motion of the horse's neck as it arches over the fence. As you get more comfortable, stick your thumbs out so that the tips touch and push down with both thumbs into the center of your horse's mane.. (Only in practice! Thumbs closed for the show ring!) This will help you to memorize how far apart your hands should be and also helps keep your hands from floating around freely.

grab mane forward on the neck, and practice 2pointing and sliding your hands forward.

Turn you hands upside down on the rains. You'll be amaized how it helps you with your foundation and how your release becomes I dependent from your seat.