Ground work is definitely a massive aspect. For ideas, I recommend checking out the Parelli ground games. There are some "natural horsemanship" trainers you may want to avoid, as clinics aren't usually the most unbiased situation to observe. That being said, I'd suggest working with a local natural horsemanship trainer if you are able. If not, it's all about time and commitment, just like any other discipline.
Like everyone else said, what are you currently doing as natural horsemanship training? It's wonderful that you're making this effort; I've been riding and training with natural horsemanship for 7 years now and it's made SUCH a difference to me as a rider and my horses!