i'm no expert, but i know what i personally like. starting with the trill at the end on measure 72, i would not start with the upper note.
Remember, I'm talking about teaching this to people who are not advanced students. Some teachers would refuse to do this, but I like to teach something, get the basics down, then return to it every three to six months, trying to relearn it much faster and bring it to a higher level of performance.
Let me skip around the whole question of starting a trill on the principal note or the upper auxliary. Those of us who are experienced can do it either way, depending on many factors.
Starting on the upper note uses 16 notes in both hands. I'm assuming we are going to play the sufix at the same speed, at this time.
But if you use triplets, you have two problems. First, you can't use all triplets. You are going to end up with 23 or 25 notes. You could still start slower, two 16ths at first, following with all triplets. But now you have a two against three problem in a measured trill. To me, measuring a trill that way, eventually quickly, is much harder than just letting the trill rip.
Instead, the first time I go through this with a student who is not advanced, which is a different story from working with someone advanced), I will stick with 16 notes in the RH because it is a "no brainer".
But if I'm working with someone who is a hard worker and wants to go a bit deeper, I will introduce the idea of just letting the trill go, freely, changing the LH:
1. Just block chords, one to each beat.
2. G, BDF, G, BDF, G, BDF, G, BDF, CE
3. GB, DF, GB, DF, GB, DF, GB, DF, CE
4. GD, BF, GD, BF, GD, BF, GD, BF, CE
By step four, I'm going to stress ending on 24 (CE). But I won't spend a great deal of time doing this, and I have a separate excercise written out showing how to do these steps in the LH.
I will also isolated the LH patterns, as written, and a free trill, going on for several seconds, to work on fluency.
Getting the hands together is the rough step. As I remember, I think I felt totally spastic when I first tried it, with the RH stuttering and the LH uneven, but as I continued to work on trills in many pieces that had the same problem, eventually it just fell into place for me and seems to do so for most students.
I want to stress that when I perform this at full speed, in a way that sounds clean to me, when I slow it down (using midi to do so digitally), the RH does not come together with the LH except purely by accident. It sounds totally wrong. Full speed, it sounds right, and it is the accenting of the LH (and evenness) against the speed of the trill that gives the illusion that it is all coordinated.
Let me leave it at that. I appreciate your answer very much, but apparently no one else is interested. I posted my almost a week ago. I had assumed that this would be a tricky spot for other teachers to teach, but I guess I was wrong.
Gary