
Copying can be a problem - right now my two adults are being gits if I walk them together off-lead, because where Opi goes Remy will follow - so if she chases a squirrel and ignores my command, guess what happens!
If I'm recall training, I do it separately, as I am at the moment. When I get it good on both dogs, I'll start walking them together again, with one on lead and swapping them, moving on to both off in particular situations (squirrel-free, hopefully!) I'm doing work with both at once in the garden as well. It's certainly helping, and the individual work on walk is going very well - they are much more attentive without a pal to egg them on, which means the recall progresses much quicker. It also means I can pay much closer attention to each dog, so I don't miss the first hints of an upcoming bolt after something small and furry, or to run off and say hi to a dog.