I use a lot of brushes. But first I use the shed blade, curry comb, then three brushes. 1) Hard brush (hard and stiff bristles) 2) Body brush 3) Finishing Brush aka soft brush) this one will bring up natural oils from the underside of the horse's coat and makes the fur all shiny:) (then I use a hoof pick lol)
I think that a thick soft bristle brush does a really great job for every day, for shows I use some coat conditioner (or even water in a spray bottle or fly spray) and spray it all over their coat and run a towel over them which gets all the dust that sits on the surface and leaves them really clean and shiny!
I found a scrubber at my local feed store that reminds me of a dish scrubber, a sponge in the middle with bristles around it, and you fill the handle with shampoo. It's definately not a last minute fix but it left my gelding super soft and shiny.
I love love love my finishing brushes. They work so well, and are a nice touch to get the last of the dust off. Taking a damp towel to your horse will also give them a nice shine. On the topic of making your horse shiny, I'm gonna urge you away from products like showsheen because they dry out the skin. Good grooming will have the same cosmetic effect without the bad side effects