Since you don’t want to add additional moisture to the frosting, I would either mix strawberry powder in just before the frosting is finished or sprinkle it liberally on top of the frosting after you’ve used it. You can get my instructions for making fruit powder here: https://www.cupcakeproject.com/how-to-make-fruit-powder-and-why-you-should-bother/

Hours? And, it’s still hot? You can always put it in the fridge if you need to, but it shouldn’t take that long to cool.