I sometimes try to do this on my own: put the dogs on a sit-stay, walk a couple of hundred metres away, throw both balls as far as I can even further away again, then put camera to eye and attempt to catch the dogs (who have long since broken their stay) with a decent panning shot as they flash by. It works much better when a willing friend is there to take over ball-throwing and dog-policing chores. 

Of course, a lot of shots still end up coming out like this:

And then sometimes there are happy accidents, like the coming-and-going one here: