I was doing an exercise last night and I felt myself just spinning wheels. I realized in the moment that I didn't believe what I was saying; my words were empty and hollow. I didn't understand the emotion behind my lines.
I took an extra second before my next line and I let everything sink in. I thought about the emotion I was talking about and let myself feel it too. The scene quickly became much stronger and more interesting. And it became more fun for me to play in - I was now invested in what was going on instead of going through the motions.
So, I like the trick of treating the last thing the scene partner said as really important. But I am concerned that it will just lead to more spinning wheels if you don't also allow yourself to really feel like it's important.
A similar trick I heard once was to just laugh or cry at the last thing that was said - even if and especially if you don't know a good reason why. You'll figure it out in a second. The reason teaching scenes, look at that scenes, or transaction scenes, et al, don't work well is because they lack strong emotional content. A lot of these tricks all have to do with injecting emotional content of some kind into the scene. Whatever you find allows you to do that is totally cool and valid.
The other cool thing I discovered in the exercise was this: I realized I was going to get no reaction from my scene partner. In this case, it was because of an awesome reason. His character had a rich albeit self-centered inner life; there was no way the character would be able to process the emotions my character was having. So I had to react to my own reaction. My character felt unappreciated, and realizing that made her sad, which made her more sad, and so on. The character wasn't waiting for something to bounce back, the character took ownership of the emotions and followed them on their own. Sometimes the scene partner who throws out a teaching scene isn't in a place to provide a sounding board for your feelings. That's fine, we don't have to wait for them to make strong character choices on our own.