I always found Repulse monkey to be one of the more difficult tai chi movements until I realized one thing
It is just chicken pecks rice in reverse. In Xing Yi, the Rooster and Monkey animals are one of the strategic pairings, so it’s no coincidence that the movements of these two animals are found in sequence in the tai chi form. I started getting the meaning of the movements when I did a deeper dive into the xing yi monkey shape applications, it really started to click when I started learning Yi Zong An Shen Pao, which contains a lot of monkey shape.
A major tactic of the fighting monkey is the grab, stick and pull off balance concept. It requires that you can use your hand to stick and pull the opponent off balance. The grip is not tight, this is more for a force that was incoming anyway. Once you stick you have to back up somehow to lead the hand backward and off balance. After that you can strike with the other hand.
This is done much closer to the center-line than an ordinary Lu, instead it is almost like a reverse lu, guiding/sticking with the rear hand.