tbforever, there is a lot of well meaning, good traditionl and respected advice in this post- however none of it has anything to do with natural horsemanship. Though this is posted in the NH section of the forum....
If you want to learn that way of doing things its probably best to get an instructor out to see you , get some good groundwork skills . You could try joining Parelli connect, it is free for 30 days. See if you liked that way, or try Quantum Savvy, Cynthia Royal, Caroline Resnick.
There are lots of natural horsemanship methods its a case of finding one that suits you.
Sorry I am unable to post any links to any further information as links always get removed.
However, I will agree that the best scenario would be to use the slower, more careful and gentler techniques to fill in the gaps in the horse's training. That, however, requires that the handler be able to first get the horse to let go of ANY aggressive thinking. And that might look a bit rough for just a few minutes before it gets nicer, but it's still "natural horsemanship".