Just like yesterday, you should be able to help your partner get a couple extra reps on pretty much every movement today, though a couple of them might seem a little confusing at first.
For T-bar rows, positioning yourself in a semi-squat at the high end of the bar is the best way to go. You shouldn't need to help much; just a hand on the end of the bar should suffice. Just watch your feet and fingers when the bar comes down!
The Day 1 video shows you how I like to assist for chin-ups. Basically, I like to provide a little platform for my partner's feet to push off of, although grabbing their calves or hips can also work.
You might feel a little silly providing assistance on the seated reverse machine fly, and yeah, it will definitely be close quarters. But that little extra bit of intensity may be just the thing you and your partner need to finally bring up those rear delts and stubborn upper-back muscles!