How do I determine if the concrete is dry enough for application?

Rust Bullet for Concrete is moisture sensitive. Even the smallest amount of moisture on the surface will cause a coating failure. One way to test for moisture is to cut a sheet of plastic in a 1’x1’ square and tape the edges onto the floor. Make sure to completely seal the edges so no air can escape. Leave it for 24 hours. Look for condensation on the underside of the plastic sheet or a visible darkening of the slab below the plastic that is damp to the touch. Both are signs of an excessively moist floor. Another way is to use a calcium chloride test kit which are sold at home improvement stores. Follow the kit directions.