If you are serious about photography (or you would like to go into photography professionally), you would have to dip yourself into retouching.
If you are into any sort of portrait, model or fashion photography, the first step you would want to do is removing acne and blemishes.
I like this video by PHLEARN. It gives you detailed explanation and lots of tips.
How is this different from millions of YouTube tutorials?
Well, it is pretty simple.
First, this is not a “copy a layer, apply gaussian blur, and reduce opacity” method.
(That’s a very beginner way with very unnatural result)
Secondly, there are more ways to deal with acne and blemishes. (Let me know in the comments if you would like to know the other methods)
But I find this method a balance between time consumption and required skill level.
Thirdly, I personally use this method if I need to do some quick retouching.
Watch this even if you think you know it all.