Frequency separation, shadow removal, powdering, freckle removal. Do you want a real person or a puppet in front of the camera? Frequency separation in particular should be used with care, or better not at all. Skin has different textures in different areas, protect and preserve those textures. Frequency separation, as well as blending textures with powder workflow, destroys these textures. Matching skin colour in different areas can also destroy the texture. Skin texture is an important part of a vivid image. Often it is enough to remove rough imperfections with dodge and burn or by using a restoration/healing brush tool.