My method, each to their own. These are blades of a 50" toro zero turn. I know, different blades, different use, but some similar concepts, especially if you have cleared the lot and you are now back to wanting a reasonable finish with what you have.
When a blade wears, the front cutting edge wears away, which makes the rake on the blade steeper with wear. So when you sharpen the blade you need to remove the material from the back to put a proper angle back on the blade. When I sharpen my mower, I normally go a little past the first pic, but not as far as the second pic. You don't need a razor edge on the blade, but you do need a rake for it to cut nicely. I grind these on my 8" bench grinder, you grind "away" from the cutting face, meaning the sharp edge is against the wheel and the opposite edge of the blade is on the rest so you are removing material front to back. You can do the same with your brush hog blades, take the back away to make a decent angle and leave the cutting face.