Hi! What adjustment tools you used in color grading and skin correction? Any tips and techniques?

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Curves for color grading
Quick Mask and curves skin correction

curves and selective color are the most flexible - though without a great eye and pretty good knowledge of color it can be hard.

with google's nik collection control points or capture one's color tools, it may save some time

The right question is: What is your goal ?
Show an example and then we can give you the proper answer.

It really depends on the circumstances, and even then everybody has their own preferred approaches. To cover Grading and Skin Correction in one question is very difficult because they are quite different issues.

But talking generally about colour adjustments, the choice of tool/approach often depends on a prior decision made regarding selection and masking. In other words, before you decide how you are going to adjust colour, you will have already thought about which colours you need to adjust, and that can mean making selections by Tonal Ranges, Specific Colours, Specific Objects or for Compositional reasons.

Curves is the most versatile tool where selections aren't an issue. And very often you'll make a selection automatically and then use it as a mask for Curves.

Color Balance is a "friendlier" tool than curves. It's very easy to control and understand, but also very limited.

Hue/Saturation gives you the most control at one visit because it deals separately with all three parameters (H,S,L), and also allows you to make and fine-tune selections based on colour range.

Sometimes a quick Selective Color adjustment is very useful.

In the end it doesn't really matter how you get the result provided it doesn't take too long and the result is good.

But if you only master Curves and Hue/Saturation you can do anything (almost!).

PS I've assumed that you would be using Adjustment Layers, as opposed to selections from the Image>Adjust Menu.