You could start with handstand backhandspring. Make sure your head is in - you should be looking towards the end of the beam where you're going, but it's pretty common for girls to look at their hands on the beam instead. Practice this on the floor. Arms should stay by the ears the entire time, no swing. Don't let the head throw back. You want to avoid a shoulder angle when the hands contact in the BHS, which will make it really hand to land.
Create a focus point for each part of the skill, but keep it simple (no long sentences). Just beginning, middle, and end. For example, through the HS support of the backwalkover, you could think "push" (strong push through the shoulders) "punch" (step down into the backhandspring) "reach" (hands on the beam) and then "square" for the finish. Alternately for a rhythm, you can just count 1, 2, 3, etc for each point your hands and feet hit, or 1, 2, 1, 2.
This is part of the reason I think it's useful to work no swing beam back handspring in preparation for series. It gives a reference point for the connection.