Fa Jin (a.k.a. Fa Jing), or "manifestation of power," is great practice for controlling and moving your energy, stretching and releasing the bows, and improving your martial arts. The force of movement in Fa Jin is a good way to begin visualizing the movement of energy during your Tai Chi practice.
Good luck! And make sure you don't move too fast or too hard, and accidentally hurt yourself. Fa Jin is about control, not strength!