The day before a show i brush my horse deeply (even shower when it is very hot so not often). I use classic brushes.
I oil the hooves. I often braid the mane and do a big braid to the tail so it doesn't tangle.
The morning of the show I just have to brush my horse and reajust some braids if necessary.
I don't particularly use special products.
And you? What's your routine?