Hmmm,well honestly, I've never tried. Not with a modern machine anyway. I attemted to sew one on with my old Singer, circa 1950. Its a home/lightweight model. The results were less than satisfactory.Broke two needles, and my lines weren't exactly strait. But newer machines might be up to the job.
A shoe repair shop does have its draw backs. Depending on how busy they are, my shop is sometimes real quick, sometimes up to two weeks. Thats a long time when the sun is shining. Also, once i had em put a patch over a pocket and the sewed the damn pocket shut. Still, the results are much better than I could do at home.