You arranged a walk with a friend and their dog, because company makes the hour go faster. 10 minutes in, both dogs are pulling, one is barking, and the leads are wrapped round your legs.
Your dog walks acceptably on their own. That is not the contradiction it looks like.
Why two dogs is more than twice one dog
Arousal stacks. Your dog starts the walk excited about the outing, and the other dog adds to it. Each dog's excitement then feeds the other, and neither comes back down.
The dogs also pay each other. Pulling gets you closer to the other dog, barking gets a response, and every lap of that loop makes the next one easier to do.
Adolescence makes both worse. Around the onset of the stage, dogs respond less to the cues of the person who raised them, and that responsiveness returns later in adolescence. Two adolescents together have almost nothing left for you.
Learning happens below the level that pushes your dog past what they can manage. A chaotic group walk is above that line from the start, which is why nothing improves by repeating it.
How to set the walk up
Meet on neutral ground, outdoors, away from either house, either gate and either car. Doorways and car boots are the worst possible starting point.
Walk in parallel from the first step, with a person between the dogs and 6 feet of space. Do not let them greet on tight leads at the start.
Start by walking in the same direction rather than face to face, for the first 5 minutes, with no conversation. Talk once the dogs have settled into the pace.
Each person holds their own dog's lead, for the whole walk. Handing a lead over means nobody is reading that dog.
No lead swapping, no doubling up on one hand, and never both leads in one person's hand. That is how legs get tangled and dogs get hurt.
Agree the plan before you leave: how long, which route, who steps away first, and what you do if it goes wrong.
Keep it under the line while you walk
Walk, do not stand and chat. Movement keeps the arousal lower than a stationary pair of dogs 2 feet apart.
Pay your own dog for walking beside you while the other dog is there. 1 treat every 10 paces is not too often in the first week.
Put distance in as soon as the pulling starts, rather than after the barking starts. Cross the road, or let the other pair get 30 feet ahead.
Take a sniffing break every few minutes, on opposite sides of the path. Sniffing brings a dog down where more walking does not.
Behaviour change is built from management plus reinforcement together, and on a group walk the management is distance and the route.
End it before it falls apart
Make the first joint walk 15 minutes, not an hour. Finish while both dogs are still manageable.
Split up at the first sign it is going: one pair carries on, the other takes a different path. That is the plan working, not the walk failing.
Do not keep going to prove it can be done. A bad 40 minutes teaches both dogs more than a good 15 does.
Debrief honestly with your friend afterwards, and decide what is different next time.
It is fine to walk separately for a while
Some adolescent dogs cannot do a group walk yet. Walking separately for 2 or 3 months is a reasonable decision rather than an admission. Meet in a fenced garden or a hired field instead.
Do your loose leash work alone, where your dog can actually hear you, and add the other dog once it is solid.
Meet for off-lead play in a safe enclosed space instead, and walk on your own.
If your dog is worse near other dogs on the lead, that is the problem to work on first. It has its own article.
Say it out loud to your friend. Most owners are relieved when somebody else admits the walk is not working.
Reward-based methods are what the veterinary behaviour guidance recommends, and none of this involves correcting either dog for being excited about company.
Safety note
Get help now if either dog has growled at, snapped at or made contact with the other, or with a person, on a walk. Stop walking them together and speak to a qualified behaviour professional who works with reward-based methods. Two dogs tangled in two leads is how people are pulled over and dogs are hurt. Keep the leads separate and your hand out of the loops. If either dog's behaviour has changed suddenly, book a veterinary examination. Sudden behaviour change warrants one, and pain frequently presents as a change in behaviour rather than as obvious lameness.
If lead walking is difficult on your own as well, the Assessment is a better starting point than any single article. It is free, takes about 3 minutes, and names the pattern underneath.
Today's version, in one line: 15 minutes, parallel from the first step, your own lead in your own hand, and home before it unravels.