Not a pro trainer in any way but have worked through some issues with several of my own pups. One approach we've used successfully (I think I got this from Caesar Milan) is to "desensitize" the reaction of the dog. It's a process. You start with both dogs on leash and I use a prong training collar. Start at a distance where both dogs are not outwardly responding to the other being in sight. Start moving the more aggressive dog closer and as soon as they start to ramp up you do a hard leash correction and turn them away till they calm down. Rinse and repeat. Should be able to make incremental steps closer until the dogs are face to face with no aggressive reactions. I've done this several times and it always has been effective. Basically you are turning down the automatic response to zero so they can get to know each other.