I still teach ex 17, but actually flying it seems a bit of a waste of time due to the need to fly it well above the heights talked about in the brief. Going down to 100 ft for a low pass over the field will often lead to a rule 5 violation, at least in my (densely populated) part of the world. A low pass at 600 ft just isn't the same. I have sometimes just skipped the flying exercise and just handled it as a ground briefing.
Good tip on timing to estimate the field length.