Step 4: Thicken it with Flour
You can add fumed silica to make epoxy thixotropic (not flowing)or hollow glass or plastic microspheres to make it light and bulk it up. Wood flour is conventional for gluing applications. That's fine sanding dust. You can get it segregated by fiber length if you crave certainty and perfection. White flour is just as good. Whole wheat flour isn't. The extra vitamins make it too greasy and lumpy.