Grooming for show days starts WEEKS before the show, in a way.
You can't just let your horse be a complete piglet then expect him to look good after 1 bath the night before show day.
I use tail wraps (but you have to undo & rewrap them correctly or it does more damage than good) and do a general groom on occasion. Rugs & sheets can keep a horse with alot of white on it cleaner. Obviously keeping a stall-kept horse's stall clean helps. My color horses are kept inside on sunny days and turned out at night to preserve their color.
Every great dream begins with a dreamer. Always remember, you have within you the strength, the patience, and the passion to reach for the stars to change the world. ~Harriet Tubman