Hiding nipples

Recently a lovely model posed for me in see-through lingerie. Now I’d

to use some of the photos but I want her nipples to be less obvious–well, invisible really. The model says that other photographers have "Photoshopped" her nipples out of pictures. But how to do that? I don’t want to pixelate them or otherwise mar the images. Perhaps there’s a way

select the darker nipple color and replace it with lighter skin tone? Suggestions please . . .

Clone tool and or healing brush?