Sharing Keynotes using automation

Hi. I have a Keynote for each of my lessons and I share them with students. I’ve got well over a hundred and want to change the font to Open Dyslexic, but it’s a pain because to change font or the masters I have to stop sharing, make changes, start sharing again.

Does anyone know a way to automate this, so I can run a script to turn off sharing for all Keynotes in a folder, for example?
I had a look in Script Debugger and couldn’t see any hooks for applescript to do this, but I’m new to that app so I may have missed something.