It always seems to take forever — those weeks of shedding out. There is no substitute for elbow grease in hastening this process. Rubber shedding curries, if the horse will tolerate it, work best, but a close second are the rubber mitts with nubs. Vacuums save labor and also do a fairly good job on hair that is already loosened. Still not satisfied' Try these:
Light: Shedding is under hormonal control that is probably most tightly tied to day length. Try leaving a stall light on a few extra hours (to total 12 hours of daylight), using 100 or 200 watts of light. It is not clear if direct exposure to sun is more beneficial than stabling the horse, but the opportunity to rub up against natural objects and roll when turned out will make the job easier. Warning: If you have a mare, she will probably start cycling earlier with this lights schedule.
Diet: Two nutrients closely tied to health of skin and hair, and most likely to be deficient in winter-time diets, are vitamin A and essential fatty acids. Feed 20,000 IU of vitamin A per day (slightly more if very poor-quality hay, less if high-quality alfalfa) and two to three ounces of virgin (not heat-processed) vegetable oil, preferably linseed, but any unprocessed oil is superior to store-bought oils.
Time Your Grooming: Hair comes out easiest when the horse is warm — after turnout or after a work. Mud can work in your favor. Dried mud traps the hairs and make the hairs easier for you to remove.
Blanketing: Use of a blanket or sheet encourages hair loss by trapping body heat and also because of the friction.