Trying to spend as little time as possible on post production means in consequence getting the shot right in the first place.
For this particular production our projector came in handy. We set it up projecting a photograph of the moon we took a couple of years ago. Displaying it from behind on a translucent background simulating the feeling of actual moonlight hitting our pumpkin.
When working with a projector you might want to use longer exposures in order to avoid problems with the frequency of the projection.
Other than that, it is pretty simple and straight forward and the best thing: Post production took altogether about 8 minutes ;)