General Antonyms:
* Write neatly
* Compose
* Draft
* Edit
* Refine
Antonyms Emphasizing Clarity:
* Write legibly
* Formulate
* Articulate
* Express clearly
Antonyms Emphasizing Skill:
* Calligraphy
* Manuscript
* Craft
The best antonym for "scribble" will depend on the specific situation.