This is a body-sculpting technique I picked up from (once again) Kevin Ames, and it’s great for trimming any excess skin from under the arms (these excess areas are sometimes referred to as “grannies” by mean retouchers).
Open the photo that has an arm you want to tuck in, making it look thinner.
© BRAND X PICTURES
Press the letter “p” to get the Pen tool from the Toolbox and click it once at the base of her arm (near her armpit); then, move to her elbow area and click-and-drag to create the second point. As you drag, the path curves. Your goal is to have this part of the path dig a little bit into her skin ...