How do I apply mastery bonuses on mirageboards that I completed before post-game?

[Togepi]

For mirages whose boards I entirely unlocked prior to post-game (when mastery bonuses became available), I can't figure out how (or even if it's possible) to still redeem a mastery bonus. Has anyone figured this out?

[Pastytastic]

If you exit out of the mirage board and go back into it you should get prompted for the mastery bonus again. You might have to transigure the mirage and back first? But should work just going back into it again.