Flourite is really messy. You might want to consider setting up little "planting containers" using cheap sandwich storage plastic boxes, then sinking those into your substrate and hiding the border of the boxes with rocks/driftwood. It'll make your flourite go much farther and keep your substrates from mixing*.
*until your cories start playing in it!
Wow thanks for the tip! I thought about making some small dividing boxes out of some spare acrylic that I have but I decided against it until now! What exactly do you mean by messy??