can't add anything to the above but I'll add a little story about a exercise I did the other day.
I was taking a pinhole picture of my car and I decided to pretend to wash it during the 2 minute exposure. I wandered around the car waving my arm around pretending to wash the car (which in fat I had just done! which covered about 1min 45secs by the time I wandered in and out of the scene to cover the pinhole. In the resulting image, I only appear in one area where I figure I must have lingered a lot longer than the rest of the time. I'm going to try this again but will have to balance the exposure with the time I take to 'wash' the car a bit better! The overall exposure was good (it was a sunny day) so I guess I'll have to try it on an overcast day to lengthen the total exposure and give me more time to slow my movement down.