This works great if you use a flapper disc with a 120 grit or so. The flapper doesn’t heat the edge like a stone wheel, so you don’t lose the temper and it will stay sharp longer.An angle grinder should do just fine. I used to use a bench grinder and just follow the slope of the blade until it is sharp. No need to make it razor sharp or spend much time on it. I only sharpen once a year, but an angle grinder is so quick you could touch it up as often as you want/need.