Bolt From the Blue sounds like a really difficult achievement, but it's not so bad. All you have to do is headshot 5 enemies while you're riding a Sky-Line. That might sound impossible especially when it's so much fun going fast on the Sky-Line, but holding back will slow you down to a snail's pace.
Once you've slowed down, you can whip out the trusty sniper rifle and pick enemies off slowly but surely. You only need 5 kills to unlock the trophy, so it won't take long. We unlocked this achievement in Chapter 24 when Booker has to destroy the turrets. Get rid of those death machines first, then slow down, aim steady, and fire on the other enemies.