Step 2: Get your USB and empy out the lego
First of all, remove your USB stick from it's case. To do this I simply used a knife to pry the two halves open, but it should vary from case to case.
Next, use the rotary disc to remove the insides of your lego piece. I did this by first cutting the middle out of the end of the lego, and then working my way down to the end. Remember to only open up one end of your lego, and only make it as wide as the USB port.
The disc is the most useful tool, because you can make cuts length-ways into the bottom of the lego, without going through the top. After doing this, tilt the disc at an angle then cut of the extra pieces of plastic.
Next use the rotary sander to flatten out all that you couldn't get using the disc. Also, you may need to thin the walls of the lego, in order to allow the USB drive to fit. The sander is useful for this too.