To be honest I was a bit curious about all of this so I did some reading over on CB's to see where they had been and what they had come up with. Bad news is, I am still curious...
The thing that makes the most sense to me would be to up your alloy hardness to begin with, as you mentioned before you coat. However how much harder is the question.
If you do not have one of the alloy calculator's they have posted on CB's I suggest getting one or if you don't want to go that route shoot me what you have to add to your alloy and I will run it to get you close to where you want to be.
Just guessing your probably around a 13-15'ish at most right now, and I wouldn't think you would want to get much higher than around a 18'ish BHN to be honest. Doing so would put you up to where your hard enough to shatter the nose as mentioned by FrankenMauser.
I cannot say one way or the other on how well mine preform on game, other than to say the I used two like the one in the write up linked above, and blew through a 250'ish pound boar, spinning it around completely to the opposite direction, then the second one returned him back the other direction as he floundered off through the woods. I fully admit that neither shot was perfect, as he slipped right up behind my grandson and I while we were sitting out deer hunting. We were not in any sort of blind, just concealed by a cedar tree we like to sit by. When the hog came up I only had time to draw my Redhawk, point and shoot. We both however saw the golf ball sized hole in his side after he spun around as the fat layer was hanging out one side and the other was obviously plugged by intestine. We tried for several hours to find him but to no avail. The next morning however the local clean up crew had and we knew why we didn't. He had crawled up under a grown over fallen tree top which was so thick underneath that even the buzzards couldn't get to him.
I have no idea how the bullets looked as well I didn't recover either one of them. I do however know that they laid a whop on him enough to spin him around in his tracks. IF they rolled back anything like the ones pictured I can easily see why. The alloy runs around a 11-12 and those are loaded to just over 1100fps from my revolver and the distance from pistol to hog was only about 20ft at the most on the first shot, and not much if anything more than 30 on the second. I hated to have lost him, but when you don't have anything to follow and when even the dog can't track him it is hard to do anything else.