It's just a matter of learning how to do it. It's trivial once you know how. You need to cover the area completely and then some (this means using a lot more cement than you think you'll need), then you have to let it dry out completely before putting on the patch, then let the thing cure for a day or so for best results. After this i usually test the patched tube for any slow leaks, either in a sink of water or by leaving it pumped up overnight in a tire on a spare wheel. This is overkill but i hate getting repeat flats.