how to teach grit?

I'm in the same dilemma, for years I've bred, culled, and selected dogs that will get out and hunt and stick with a runner in the process losing the grit in my pack, now im of the school of thought that there are " rough" dogs and then there's dogs with "grit", the latter of the two being able to stop a hog and keep it bayed without repeatedly trying to catch it and continuing the running. I've been talking to a guy who was once a member of this forum who is developing a line of dogs that are bred specifically for speed and stopping power, within the next year or so I'm going to need an outcross and I'm going to add some of his stuff, to answer your question I don't think that is a learned trait, now I believe you can maybe sharpen their skills some but In my opinion your not going to be able teach "grit" to one.