Is it possible to get a nice consistent matte on a mold surface with abrasives? Maybe sand to 3000 or 4000? Steel wool? Any other options? Also if doing this, will mold be more sensitive to sticking prepreg parts (using frekote). 
Second question, what about prepreg matte carbon fiber sheets? Would normally use plates of glass. I've seen glass with a matte looking finish, but can't find it when searching for matte glass. Not sure what it would be called, or if there's a different material that should be used.