Takeing loose dirt and mixing in compost isnt topsoil. If you are really talking about building topsoil, expect it to take some time.
A decent portable screen can cost around $30 grand. With the screen being portable, you can take it to the site the soil is being removed from and screen the materials there. This allows to sort the real topsoil from the plain dirt instead of having it all mixed together in a big dump. This means haveing to have a loader as well as a dumptruck to transport the screened soil to your site for storage as well as for hualing off the waste.