studio practice

I used two ab- 800 with shoot through umbrellas behind subject on each side shot at full power. To the left of the camera is a 580ex-ii with a shoot through umbrella at 1/4 power. I am not really good at using a white background and read somewhere to try this method. I am shooting in a small room so the walls are reflecting the ab's light. I still don't know what else to do to make this type of photography work. Any suggestions?

Done