Hasselblad Pinhole

I've been thinking of getting a pinhole body cap for my Hasselblad but I can't figure out how one would expose the film. Simply release the mirror, which would open the back curtains and close them again by returning the mirror? That would induce lots of vibration, would it not? I guess you could block the light with a finder until after the mirror was released, and use a finder again until the mirror was returned. Any thoughts?

I wish I could find the picture to show you, but I set up my 501 with a pinhole cap and sport finder... the one that looks down on on the GG. Use a cable release, locking as needed, or press-and-hold shutter release. With a tripod and solid head vibration isn’t an issue.

In that configuration I call it my HoleyBlad, and at least one person has referred to me as a HassyHole.