I have settled on yellow DMC satin floss for the main body of the bird. It’s bright and shiny, and very easy to obtain. I’m going to see if I can get a smoother effect with some thread conditioner, and maybe try to use a laying tool. I’ve only started the first layer – I haven’t put down any couching lines.
Méri (who inspired this project) went to visit a museum for more information on Castelo Branco embroidery. She is writing a series of posts on what she learned. So far there are three posts with some nice photos and information directly from the experts. Apparently what they actually use at the moment are lightly twisted Italian silks and a heavy 50% linen fabric which is similar to the traditional linen homemade fabric. Also, the couched lines over the top do not have to be straight – sometimes they are worked in patterns. For more information, see Méri‘s blog (I have linked her first three posts on the museum visit directly).