Try NOT to use the Xbox 360 controller for this achievement. Using its ridiculously bad D-pad is an exercise in futility. The design of the D-pad is so wretched that it stretches what normally should be a two-minute task into something much longer and tedious, through no fault of your own.
If, however, you don't have anything else to use (guitar controllers, fighting/arcade sticks, hell, even actual DDR mats are better than the 360's D-pad), and you're stuck with the stock controller, here are some tips:
1) Do NOT make diagonal presses. Make sure to press down on the edge of the direction you want. It's raised, so it'll give you less of a chance of hitting another direction at the same time.
2) Use both both your thumbs if you must.
3) The only time you'll need to hit two directions is for LEFT and UP. And instead of trying to hit two directions at the same time, hit them one after another.
4) Use your health bar (awkwardly placed at the bottom of the screen) as a gauge for mistakes.
Hope that helps. If you're stubborn like me, you'll end up wanting to beat it WITH the D-pad, so you'll have memorized the placement by the time you actually get the achievement.