Probably not as much masking as you would think, Jim.  I'm betting PeggySue probably does a gross deletion of large areas and then refines it by masking.  At least that's what I do.  Saves a lot of time.
PeggySue - The finished product on this could easily sell as a fine art print.  The Arabian people would love it.  I know I would.  I bred and showed Arabians many years ago in a previous life.  Went to the Nationals many times when it alternated between Scotsdale and Louisville.  I think it's always in Scotsdale now.