There a very easy way to do all the fast forward achievements.
On the main menu on the bottom right, click on the options button.
The third option down is a Fast Fwd Speed scroll bar. Drag it all the way to the left.
Essentially you just made Fast Fwd normal speed.
The last thing I recommend is to play on either Cyclone Island or Cargo City, as there are the easiest levels.
***Don't forget to hit the Double arrow in the top right corner to activate Fast Fwd!***
Also note that pausing the game or accidentally hitting the stupid bing button (On my LG Quantum) will take you out of Fast Fwd so remember to hit it again. You know you are in Fast Fwd mode when there is a single arrow in the top right.