Fog Effect in FCP?

In iMovie there is a fog effect--a bit heavy-handed, but for a specific project of ours it would be useful. Does anyone know of any way to achieve the same effect in FCP? We have the Nattress filters, but their Morning Mist filter seems to just be a uniform wash across the entire image, with none of the patches and drifting of a good fog.

Thanks for any input.