This^ removing the fog light from the vehicle and applying makes it much easier. A heat gun also helps a lot.It is very difficult to get it perfect on that curved surface. It is much easier to get it closer to perfect if you remove the plastic bezel that surrounds the fog light so you can get at the edges better. A heat-gun is also very helpful to smooth it out. The reality though is that no one but you will ever be down there 6" in front of them inspecting your work, so I'd suggest not worrying about it. From normal distances no one will ever notice. They end up getting beat to hell with rocks and debris anyway, so you will get the opportunity to try again in a year or so.