Painting Is Easy When You Don't Know How, But Very Difficult When You Do. Edgar Degas

I think that quotation applies to more than oil on a canvas.  Dan the painter is trying to keep up with our last minute changes in room colors and at the same time stay on schedule.  The primer is being sprayed on now, after that, two coats of flat finish.

Dan spraying primer on the ceiling in our bed room on the first floor.  He's been doing this for 35 years.  I think he knows all the tricks; see below.
 

Here is Rick and Crista's bed room on the second floor after it has been primed but before being painted.  Notice how Dan has tinted the primer the same color as the room will be painted.