It probably won't work in a charge Wolfhound.
There's been a lot of information posted here. Some good, some bad and some just experience.
I have a lot of experience with Black Bears and none with Grizzlies, never seen one, just pictures.
From what I've read, Grizzlies often bluff charge.
From my experience, Blacks almost never do. The one's I've seen charge, mean it.
It's unbelievably fast, much faster than any dog I've ever seen.
Assuming no wind, the maximum practical range of bear spray is about 12 feet.
Hitting a charging bear at 12 feet with spray is useless. Just his momentum will make him run you over.
In a charge, shoot him, aim for the nose which will hit the heart if you aim right but generally people shoot a tad high when stressed so a high shot will catch the brain.
About the only time bear spray is useful on bears (I like it for people, it's hotter) is when one is nosing around camp or the picnic basket.
My point is, if you're close enough to use spray on an angry bear....better shoot him because you won't get a chance to do both.
I also want to restate that being in that situation is extremely rare. It's like being bitten by a snake, On a normal hike, you walk by dozens and never know it. They just want to hide or get away.
This one would have been a candidate for spraying if I hadn't been aking pictures, but way too close if he was mad.