Sharpen with a chainsaw file. Work great on deer - especially when skinning out the legs as mentioned above. I also use it to unzip down the spine when I am boning out a deer where I found it, which I often do anymore. No need to take the bones and hide home and then turn around and haul it back out to the woods after I butcher the deer. As far as hogs go I have found gut hooks are not so good. Hogs have seriously course hair thats often very full of dried mud - this bogs the hook down and makes it a real pain in the butt. Go with the sharp blade two finger method on pigs. Also, a tip from an oldtimer I have used exclusively is make the gut slit from the chest down not the pelvis up with either blade. you are going with the grain of the hair and it works better and keep a lot more hair off the meat.
Bob Urban