Thanks, Carl. Your skills are an order of magnitude above mine.
Yes, I made a lot of the mistakes you mentioned, but- about panning- there really isn't time or room for that for an airplane traveling along a reciprocal track. If ATC mentions the traffic (more for interest, since separation is adequate if everyone's doing what they're supposed to be doing)- you won't actually see the aircraft until he's well inside 10 miles. That's less than 40 seconds from when he starts out as a hazy dot until he disappears over (or under) your windscreen. It's only the last 2 or 3 seconds that he's big enough in your field of view to produce a useable photo. You aim, you shoot, sometimes it works, most of the time it doesn't.
Crossing traffic is easier as is the organized track system over the Atlantic where everyone's stacked up and going in the same direction. (But I haven't flown either big ocean since before digital cameras were available to the masses.)