The short version of the answer to your question is that you do it both "in camera" and in post-production.

A longer answer breaks out into a few thoughts:

In Camera

1. Light the subject correctly. I really recommend using an incident light meter (a decent hand held one) to calculate the correct exposure for the subject rather than relying on the reflective light meter in your camera. This enables you to keep lights and darks correct rather than relying in the camera meter to pick the correct middle ground.
2. Get the correct color temperature. If you know what it is, and your flashes are accurate in temperature, then dial it in. Otherwise use a gray card to get it.
3. Makeup. There's a reason that professionals use it when under the lights, male or female. Makeup, especially foundation, helps to even out the skin tones and allows for contouring and shaping before you put light on them. A good makeup artist is really going to lighten the load on the post-processing side.
4. Comfortable temperature with the subject having sufficient time in location to have warmed or cooled appropriately.
5. Avoid clothing or accessories that apply pressure and are going to be removed before shooting. Otherwise give time to let the pressure marks fade.

After the Fact

1. Noise reduction, especially luminance, will blend and drop detail which will also smooth out skin tones. Do it carefully and use layers and masking so that you only effect what you want to effect.
2. Cloning good tone from the skin to the other parts is a pretty common, option. Do it slowly and with a ligth hand. Layers help here because you and opacity adjust as needed.
3. Dodging and burning, slowly and with a light hand, can even things out.
4. Frequency separation techniques allows you to work on the tones of the skin without impacting the texture. The linked video from Phlearn is a good place to start with learning this technique. It's quite powerful.
5. Portrait editing plugins to your favorite editor. I use Photoshop and Lightroom, so there are a ton for that. If you use something other than Adobe products, look around, but some of them offer a plug-in that also comes with standalone functionality. Word of caution, really soft touch with these is needed, they can be just way over the top in their changes if you're not careful. When I have used them, I pretty much turn off everything but the skin editing features.
6. Desaturate it. Nothing wrong with a black and white portrait and desaturation coupled with a bit of dodging and burning can turn a shot around quite nicely.

I'm sure that there's a ton more people can supply, but that's some of the things I've done or considered when it comes to portrait/people.