There are many variables as another poster said.
Yesterday I ONR Wash n Waxed my 350z, including the tire/rims (not barrels and just a little on the wells) in about 20 minutes or so. I do it in my garage, out of the sun and I don't do just one panel at a time. That is a complete waste of time if your car just has primarily only dust on it. I wash all the glass, the pillars, and the roof (so the whole top half of the vehicle) and then dry it. Lots of times I'll include the hood in that. Then I do a side and the rear bumper, then the other side, and almost always do the front bumper last. My front bumper is in terrible shape, the whole thing is extremely rough from rocks, bugs (wasn't always an AutoGeeker), and someone backed up into me once and marred it up. You can't even tell really though, because the paint was so bad to begin with there.