Okay so I think I'm sold on
sjh953's "reach behind you and fog them out with pepper spray while they're chasing" technique. Seems like the least risk of getting bit while actively deterring the attack.
My friend isn't confident about the pepper spray method tough, and thinks we need to find something else. I guess he was a little more traumatized than I was.
His logic is "well the pepper spray fog technique only works when the dog is chasing. How will you get the pepper spray once the dog takes you down?"...which I suppose makes sense, but it still seems like it's probably the safest option for dog defense while still being effecitve..