It's not often I want advice but now I do. 

We always let our senior dogs help train our new dogs. It's time. 
Faulkner is rapidly becoming not a senior dog, but a geriatric dog. 

I found a dog. Small pit/shep mix, F, abt 1 yr old. Not aggressive with people and will meet Biscuit, my beagle/basset 2yr old, tmrw.

I'm at our Ohio vacay home. Next wk I rendezvous with Hardi for an overnighter. I want to swap Biscuit for senior Faulkner, now that her training program is set, and let Hardi work with her while I socialize Faulkner with Newbie, here, where I have my scooter to exercise/tire/calm them. 

I use a sit-before feeding method of reminding our dogs who is boss, and I have worked with dominance-tending breeds before. I'm strong enough to manhandle Newbie on leash, and I have good separation here for a gentle intro period.

When I take Faulkner and Newbie home, I can teach Hardi what I 
learn about their ability to cooperate.

Does this sound crazy? ;-)