Well it all depends. Is there a lot of light colored hair that you need to dye or is the calf solid black and your just tring to cover up highlights or calf hair. If you have light hair then it will start to bleed thru in just a few days. Also, are you gonna spray paint on the calf and have to break the paint down? The more you have to use soap or alike product the sooner the color will wash out. I would dye the day before first show and then use paint the next week on spots that have faded out. He will look best first show but you should get by ok the next week.