For applying Hoof oil / Hoof flex on your horses hooves, you'll find a small sponge works just as well as an oil brush.
Old Horse Fly Masks make great wound covers and keep the flies off your horses' legs while still allowing the air to circulate to heal the wound.
Horse Brushes that do double duty? Nail a few old horse brushes (the bristly ones) to the sides of the stall so your horses can rub against them to get at those annoying itches.