Please read mysticwolf83's solution first before reading mine, as he goes more into detail on what you need to do first, before you can even attempt to unlock this achievement.
If you can't get the achievement by sliding, what you can do is use any object that is long and easy to hold. Place the object on the far right or far left of the keyboard and quickly move it across, making sure you hit every key. I used a broom, but you could probably use something else. A mop, long stick, anything. Good luck, and I hope this helps.