Well, I'm going to actually answer your question. This is THE book for show grooming:
This is another favorite: http://www.amazon.com/Show-Grooming-Winner-Attire-Breeds/dp/0914327127/ref=sr_1_3?s=books&ie=UTF8&qid=1350964725&sr=1-3&keywords=horse++show+grooming
Though skimming through the other posts, you might just want to go with something more basic. Simply Google "horse grooming" and I'm sure you'll find something of use. Or check out a basic horse care book, most have a section on grooming.