One option is to throw the old pair out and replace them. Or, you could buy a sharpener optimized for this dual-bladed hand ...

This is awkward with garden hand shears because of their construction and the relatively small blade size. What you really want to do is take the sharpening stone to the tool. Diamond stones (or ...

but to sharpen by hand requires patience and skill. [CNC Kitchen] instead decided to use technology to get around the problem, designing a 3D-printed tool to make the job easy (Youtube video ...