I actually never saw a grizzly during my two year sojourn. But one time three of us were hiking down off of a pass, and going through that thick brush between tundra and timber we were following dinner plate size bear tracks in the soft trail. You couldn't see ten feet in front of you and less to the sides in most of that stretch. I was the "gun guy" of the trio, so I got to take point with the shotgun. Being safety concious, I kept the chamber empty and figured I could rack the slide.
Looking back, I was an idiot 
I should have had one in the pipe and the safety off with my finger outside the trigger guard. That's the only way that I would have had even a chance of getting a shot off at a bear in that thicket. 
Yeah, that's the time to have whatever you have in hand. In that situation, making noise, I'm going to assume the bear that didn't want trouble already left so I'll be holding the gun.
Spray to me is more of a "you see the bear a ways off and it casually decides to get closer than you are comfortable after you do the make noise and look big tactics" deterrant.
