The 6-traits of writing hold true for all languages. The early research was conducted in multiple languages and found to apply. I did a quick search for Spanish Language resources on the NWREL site. (To see everything click here.)
NWREL has a Spanish language scoring guide for you right here:
Here are Spanish language lesson plans:
There is also Spanish language scoring practice at:
Spanish teachers! I know this approach, combined with a writing process based workshop will work for you!