Re: Calluses - How do you maintain your fingers?
Based on what I'm seeing in that pic, I wonder if using an emery board would be a more controlled way to reduce them? Cutting/shaving calluses can be tricky business (I've only done it on my feet, and accidentally cut too deeply once or twice).
Maybe get 2 emery boards... 1 pretty rough, and another that's finer. Hit them first with the rough one to knock down the bulk, then finish it off with the finer one to remove any ragged pieces of skin that might be hanging off.