I have used a very thin file to touch up these tools . it takes a bit of
skill to hold the file steady but it can be done .

If you can set the tool in a vice you can also use a dremel tool with a
cut off wheel . The cut off wheel is super thin but once again it takes
good skill to set the spinning wheel on the blade & get it streight .
Dont draw the wheel across the blade .. lay it fully on the blade and
hold it so it does the entire blade edge in one shot .