RE: grunt call question
You can but it could be deterimental to your hunting. For every buck you call in, you'll push one off as well only because of a possibility of a larger buck, the current mood of a buck or different scenerios. Grunt calls can work magically but at times they don't necessarily work either. I'm not sure you want to either accept that fact you may push off a buck.
I usually only call when I see a deer that way I can watch it's reaction and read it's body language. That tells me to change calls, tone, reflection or tactics.
Good luck because it can work but be subtle.