Below is a device that greatly eases dog-toenail clipping. Specifically, it is a thimble (100) that fits over the shear(22) and adjacent parts of a Resco clipper (20). The thimble is secured by a tiny dab of gum (24) under the rear edge.

If you have a 3-D printer or a friend with a 3-D printer, then you can use the .STL file accessed by this download button.