With warped watercoloring, when dry, I have placed the piece between 2 pieces of text weight paper & ironed. Then put some heavy books on top until piece cools. The text paper seems to absorb some dampness from the watercoloring.
I never thought to try this with perfect pearls. I would wait until it's dry & perfect pearls are set or they will transfer to the text paper. Maybe heat will draw out any remaining moisture cause them to transfer. Worth a try though.
I hate that you have to mist perfect pearls. When originally marketed, that wasn't necessary. But when the perfect medium pads were disintigrating over time, I'm guessing they had to reformulate the ink which didn't set the perfect pearls, hence the need for misting.