Give a lot of bubble baths it really helps!!
Rubber! Rubber lifts and takes off massive amounts of hair compared to normal brushes. I give the horses a quick brush with a plastic curry comb to get rid of dirt stuck to the hair. Then I give them a good brushing using a rubber curry comb in a circular motion. Then I give them a sweep over with the rubber side of a dry sweat scrape. Finally, when I'm finished/tired/bored/choking, I give them a quick brush with a soft brush to get rid of the most loose hairs.
It does send hair everywhere though so don't wear fleece and take the horse out of the stable!