I 2nd the idea of having a citronella spray around. While I would NEVER encourage any type of harmful discipline, etc., since there is only 1 of you and 2 of them, breaking up fights such as you describe can be almost impossible. I know, because we have some fighting issues in our household. Another thought is keeping one of those air horns around (like some fans bring to sporting events). Will certainly be loud enough to distract them temporarily.
Another thing to try when this happens is shout "who wants to go for a ride"..... "who's here".... "go for a walk"....."who wants some ice cream" or some other phrase they recognize/really like. While I haven't tried it yet, the thought has crossed my mind. Of course, I don't know if they'll hear you or even pay attention to what you are saying in the heat of the battle. But if it stops the fight when you are alone, so much for the better.
Also, I would suggest another book by Jean Donaldson, "Mine - A Guide to Resource Guarding". It may be of some help.
Above all, as also suggested, read The Dog Listener and practice the theories to the maximum. Establishing yourself at Alpha does work wonders!
Good luck!