and fill over the top of the concrete mix with dirt, tamping in place like you would a post without concrete in the bottom. There's enough moisture in the ground in most places to cause the chemicals in the quikcrete to activate and set up.

I've never had an issue with the quikcrete failing to set using this method. When I've had to dig up posts set this way, the concrete at the bottom always comes out in one piece around the post looking exactly as if the concrete had been mixed with water.