You are not going to have to take a weekend to make something for the co-worker.

"I'm sorry, I can't do it."

Repeat this mantra as often as needed.

"I'm sorry, I can't do it."

"I'm sorry, I can't do it."

"I'm sorry, I can't do it."

"I'm sorry, I can't do it."

You could also remind flyer co-worker that Mouth of the South is not your boss and that you are busy with work that your actual boss needs. Flyer co-worker can ask his boss for help. Or: flyer coworker can learn to do the work himself!