>>292757181
go into blender and delete the vertex groups corresponding to the leg bones.

not sure what you mean by adding shading to a place that "has no geometry". you can bake ambient occlusion in blender which will give you a texture of shaded areas i guess, but that depends on having triangles with UVs. For specular highlights, those are dependent on view direction anyway, so you're best off using a shader, or just hand painting stuff that you think always needs to be there like cheek shine.