If you have thick, dark whiskers and fair skin, there will be a shadow. Unless you've used other shaving methods and had better results, I doubt that it is anything you are doing wrong. Plenty of guys have a light shadow (myself included), even when well shaved. That said, you could *try* a sharper blade, a second ATG pass, etc and see if it helps a bit. Also, try a softer brush (sounds like you are using boar, which I personally like, but which isn't as soft as a horse or a higher end synthetic or badger) Some guys get brush burn from scritchy brushes.