I got the avatar using a plan rolly ball mouse with a long annoying wire. I made sure it was all cleaned out first, then ditched the mousepad, made sure the desk was clean, and went for it. If you have an optical mouse, it's probably easier, but not impossible without one.
It helped me to focus entirely on the looped end of the device and imagine it as a three dimensional shape passing around the wire. Its a lot easier to maneuver it around curves and corners when you can visualize how the loop would move if it were 3D instead of a 2D flat picture. I kind of pretended that I could see through the wire and see the other end of the loop.
I also played on a large screen mode, and turned the sound all the way down. Dont worry about the time bonus at all either. You dont need them to get the avatar score.
An NT article has a guide for the game here:
http://neopets.com/ntimes/index.phtml?section=158277&issue=220