Soften Skin?

Click on the Adjustment Brush (K) in the toolbar near the top of the Develop module’s right side Panels area, and near the top of the panel, immediately to the right of the word “Effect,” you’ll see the word “Custom.” Click on it and a pop-up menu appears with a host of presets put there by Adobe with ideal settings for particular tasks. Choose Soften Skin from this menu (as shown here), and it puts in some pretty decent settings for skin softening. Now, all you have to do is take that brush and paint over your subject’s skin to soften it (while remembering to avoid detail areas, like their eyes, lips, edges of their nostrils, eyelashes, eyebrows, and hair).