I use a #9 Embroidery and whatever cotton thread I have that matches. I prefer Sulky or Metler - haven't tried all these new threads that have been coming to the forefront. Don't like Metler for machine as it's really linty, but it's fine for hand applique. I'd use silk if DH had a job. Don't really like Coats & Clark as it breaks too easily from being in a needle with a small eye.