Liquify is another tool that brings out controversy but it is just a tool. The user decides how to use it. Nino uses liquify for corrections and stylistic choices, and done with anatomy/physique kept in mind.
Retouching eyes is a delicate thing - go too far and you can destroy your whole image. Learn Nino’s “less is more” approach to retouching eyes.
Learning to use Nino’s included actions to add textures and noise to your images. A wash of noise can really help tie an image together.
What is a secondary correction? Nino will often pause in his workflow after he has done the majority of the heavy skin work to take a second look at all the colors in the frame. Getting certain areas under control will allow the image to take the color grading even better.