1. There are books on Photoshop that teach you how to do cloning, healing brush, slim waists, enlarge breasts, remove double/triple chins, etc.
2. If you do darkroom, then you can still use a fine brush and spotone in addition to dodge and burn.
3. Of course before you even enter the darkroom or Photoshop you can use a Softar filter. As Zeiss says, each grade takes away 10 years.
4. The real question is-- do you really want to do all this? Will the end result be real? I've been repulsed by studios offering "makeover" packages where the results are so fake, the skin is so obviously plastic, the diffusion effect is so strong, etc.
5. My suggestion is to do what you can in terms of clothing, posing, lighting and camera angle to hide/minimise the flaws and let the rest be. I remember well the portrait of Condoleeza Rice in a portrait photography book I bought. She is frankly not a very pretty woman, and the photographer did put the more pimply part of her face in shadow, and the side lighting created a mysterious and powerful look that was appropriate for a Secretary of State. Not pretty-- she's never going to win a beauty contest-- but it was a well-executed formal portrait.