I don't remember who first showed me this exercise, but I've really enjoyed it. It's a different take on some of these ideas:
Uke and Nage start with arms at the places where the two arms meet in a shomenuchi attack (there is name for this position, but I can't remember what it is: arms crossed as though Uke had just done shomenuch and nage was just about to do ikyo). From this static position, Nage does ikyo twice: once right and once left. Then they switch, but not in the sense that they switch Uke and Nage. Instead, now Uke is the one 'doing' the ikyo on themselves. That is, they move themselves through the appropriate Uke positions for ikyo, and Nage follows along with a feeling of effortlessly performing the ikyo. You do this again, once right and one left. Then switch Uke and Nage and go through it all again the other way.