Until I sold it, I was using my old Sima Soft focus lens. You had to slide a tube back and forth to focus it. You then put different sized rings in the front for the fstop. It was always difficult to focus (especially since it was soft focus) but there is a way to cheat. Even with a manual lens, if you watch the little green focus confirmation light, it will light up when the camera thinks you are in focus (at least my 20D works that way).
If you decide to change out the focus screen, then you need a special tool (super hetrodyned magic oscillating projector) sometimes known as an eggbeater [img]/ubbthreads/images/graemlins/grin.gif[/img]. Wait a minute, I think I'm thinking of an old magic trick, so scratch that last idea.
Here's an old soft focus image for you to look at: