For my shelties (white feet and ruffs) I always use horse shampoo for white horses, cant think of the name off hand I get it at TSC (farm store) it is a dark purple/blue color. Really makes the white fur shine!
My friend that shows irish red and white setters uses Chris Christians white on white, and ice on ice
Zelda- "Twilight Princess Von Hemlock"
Gryffin- "Gryffindor Von Hemlock"