As mentioned before the putty will get more firm but it will never completely harden.
How to use wood putty to fill screw holes. Pick up a scoop of the wood filler on the end of a putty knife and work it into the crack or hole. Make sure the crack or hole is completely filled then scrape the blade of the putty knife flat across the surface of the wood to level off the wood putty. The craft sticks will act as a support for the wood filler. Repair a loose screw using sawdust and mister glue in seconds.
Use vinyl spackling compound or water based wood filler to fill small holes on interior surfaces. Screw bends rather than coming loose all with in a minute or two. When applying wood filler over fill the hole slightly to compensate for shrinkage as the filler dries. First clean the wood you want to fill with the wood filler.
The filler should be level and even with the surface of the wood. Once your wood filler is mixed use it quickly. Apply the wood filler to the craft sticks to fill the hole. Wood putty is easily applied with a putty knife or a finger if the area is small such as covering a nail or screw head.
Bits of dirt dust paint chips and wood particles will only stand in your way of getting a pretty smooth finish. Trim off the strips with a sharp knife or chisel if they re sticking out of the hole and sand the area if necessary use an awl or drill with small twist bit to bore a very small pilot hole into the filled wood then drive the original screw into the pilot hole. Mister glue can be used to glue almost anything to anything. Once the filler has hardened sand it smooth and prime and paint or stain as desired.