The moment that someone blinks there's a moment of disorientation. You have to use that moment in your favor and move so that they can't predict where you are. Once a blinker lands they can only blink one more time, so wait for it and move again (if you can or haven't killed them already). the moment they land from blinking is when you shoot. You don't shoot before they blink because that's what he wants. The easiest kills for blink shotgun are people that are aiming down sights and standing still. If a blinker sees you shooting him from afar aiming down sights it doesn't take too long to run and blink toward you and rain down a shotgun to the face, but if you move the moment that he blinks he's now lost and you can shotgun him yourself.