Each flash will serve a different purpose rather than just fill.
you gotta learn how to use and have a purpose for each one.
One flash at a time.
Start with your fill light and take a quick capture to see how it looks.
Brighten or lower it if you need and check that you are happy with the results.
From there, move on to the key light, or the rim light.
Adjust accordingly and see to it you are set before you move to the next one.
Have the athlete help you if the location is tough or you are far away.
One Vivitar 285 with purple gel for front effect.
Shooting a large jump?
Experimentation is important to find out which setups will be the best.
Become one with your flashes.
One SB-800 to the left and low aimed up at the athletes side for rim lighting.
Triggered with PocketWizard Plus II's.