Thanks Ralph,

I got this procedure from the Hassey User's Group:
With a 500 series body you can in theory make due with one cable release on the Prontor, but it would be easier with two, the second for your body's release.

The procedure would be like this:
1. Open the Prontor shutter (B exposure) with cable release and lock.
2. Focus.
3. Close Prontor shutter by unlocking the release, and set proper/desired exposure.
4. With a second release open the body's aux shutter by pressing the release, or alternatively, prefire the body (mirror prefire).
5. With the aux shutter open then release the Prontor shutter using the cable release.
6. Release the body's shutter or unlock the cable release on the body to close the body's aux shutter.

I guess I would add the disks after focussing and see which one gives me the effect I like.

One more question - which f-stop do I use? If the disk has an f-stop of f7.7 and the shutter an f-stop of 5.6, I assume the f5.6 f-stop prevails, right?

And with Bob's links I think I've got the whole idea of this thing. Now to give it a whirl.

Regards, Art.