I did it by using the flipper ability on the first level that you get the flippers. It's pretty easy to keep the ball alive and hit a lot of the pegs with one of your earlier shots. I was able to get 3 free balls just off of the score (125,000 points). I imagine that it would be pretty easy to get 2 free balls with points and then hold the ball on one of the flippers until the free ball bucket comes down and roll it in there.