... There was no planning involved. Nothing formal. We simply worked this out. Easy when you've spent a lot of time diving together, and you have similar diving styles.
At the risk of belaboring, let me add that you and your buddy really should have an agreed upon plan for what to do in the event of buddy separation--rather than pretend it won't/can't happen because of this or that technique or gear.
My GF-turned-wife and I were trained by the same hardcore dive instructor (though a couple of years apart), so our response to this kind of thing (buddy separation) was ingrained in us. We never had to discuss it.
I posted on SB several years ago about my first buddy separation when diving with an unknown buddy. This was on a deep wreck off of either Grindstone City or Port Sanilac (IIRC, without digging out my old log books). She was an experienced deep diver. I was still relatively new to deep. We were both in doubles. Limited visibility on the wreck. We were meandering along the rail when I paused to scrutinize something. Paused a little too long (probably a bit narced), because when I looked back up, she was gone. I couldn't see her at all. I remember thinking, "Hmm, we didn't discuss a plan for this. I think she'll be back, though."
I hovered in place for a moment or two and then she meandered back o where I was. Okay? Okay! Dive continued, no beats missed!
A plan would have been better, though.
I had another buddy separation a couple of years later, that really should not have been possible, on a much deeper, much more serious dive ("Kamloops", Isle Royale MI). That one was scary. I think I posted about that one, too.
Bottom line: Train so that buddy separation is less likely, but have a plan in case it should happen.
rx7diver