Loose Leash with Mult Dogs

Gah! I'm getting frustrated! Need some advice/encouragement. . .

When separate, Missy and Maddie walk very well on a leash... they both know heel, and typically never pull on the leash.
They both naturally heel toward my left, but I was working with them for several months to heel to my right on command (left="heel", right="side") so I could eventually walk on on my left and one on my right. They also both know when I release them ("okay!") they don't have to heel, but they still need to walk loose leash.

My problem is trying to walk them together. They can walk one on each side in the house and in the yard, but one a walk they feed off each other's excitement or something. For the first quarter of the walk they take turns yipping excitedly I only walk them together at dusk, and this is their second 25min walk a day... in addition to other play, ball throwing, backyard zoomies, what have you. [Their first walk I walk them separately, because I walk with a friend and her dog also.]

The yipping generally stops when we get going and turn the first corner. However, the PULLING doesn't. Usually, one of them pulls and I work with them and get them to heel. While I'm going that, the other one starts to go ahead (which is fine as long as they don't pull) and by the time the first one who was pulling is finally not, the other one starts to pull . . . etc etc
More often than not, I get Maddie to heel to my left, and then I struggle with Missy for most of the walk to stop pulling, and Barking at other people, and (mostly) dogs. She does this even when I get someone else to walk Maddie with us (rare occurrence, but I can get my brother or friend occasionally). She doesn't usually bark at others on a walk without Maddie... she'll walk nicely on a walk with my Dad's dog... but I'm having problems with walking Missy and Maddie together, in general. Oh, and when she barks at dogs, she sometimes gets Maddie doing it as well . . . *takes deep breath*

I'm considering putting the Gentle Leader back on Missy, just for walking them together. I hesitate, however, because I haven't used it with her for so long and it took her a long time to get used to it - she doesn't like it very much and has been known to howl like I'm killing her. opcorn: lol

I'd appreciate any tips/suggestions !!! TIA

I think it would be a good idea to go back to doing whatever it is you did at the beginning of their individual leash training - use a clicker, treats, head halter, harness, whatever it is that taught them initially how to walk with you. I think the problem is that walking them both together is SO different in their minds than walking alone, that it's basically a brand new behavior that you'll have to train from scratch. Of course it probably won't take as long, they'll probably catch on quickly because they had been introduced to it before.