What you did worked, and it's hard to improve on that.

The use of pepper spray could be a lesson to the owner: doesn't that smell linger? Two large dogs reeking of pepper spray in the Cooper grin. Most people of that ilk only respond (learn) to what affects them personally.

Approaching dogs that don't seem to be attacking may respond to a low, firm 'Sit!' But if it doesn't work immediately, it usually doesn't work at all.

Dogs that have learned how to work together to hunt and one starts to circle behind you are an incredible danger. If I were armed, I would take them down ASAP. The one in front will try to grab the muzzle of a deer/sheep/goat/calf, the circling one goes in for the hamstring. I have often wondered when I hear of a child being bitten in the face if that wasn't the first instinct on how to take down prey.

I am wondering if firing a shot into the ground would be effective at all? Scare them off? Make them worse? But I do suspect that it might kick up the IQ of the owner a couple of points...