Tell him to find a concrete worker and offer his about 200 to put a professional finish on the track on a weekend. He'll be very happy with it. With Concrete it's easy to float it out too much which will turn the top 1/4 to powder when it dries. Also it's easy to not float it enough. Also the tools to do it are expensive and a current worker can probibly borrow some from his work Including the Gas powered surfacer that'll put that final touch to it.