Want to learn retouching?
I know this has been a question that has not only popped up for me, but for several photographer friends of mine. A newer photographer will send them a link to an image or an ad promising to make them a top notch retoucher if they only buy their product, and ask "can you teach me how to do this"? The simple answer is yes we can teach you how to retouch, but the question is how much time do you have, and are you willing to dedicate the time, effort, and resources into learning how to do it well? To break it down, nearly everyone that has reached out has had zero experience using photoshop.
This means they will need to spend 5 hours(on the low end) to learn the very basics of photoshop, and about 20 on becoming proficient at those basics. After that they will need to spend even more time learning some more advanced things like color theory. A base knowledge of color theory will not only help you with retouching (knowing that adding cyan will reduce reds in the skin) but will also help you learn about color grading which many consider to be part of the retouching process. To really understand color theory to the point where you can recall the knowledge will take more practice, lets call it another 5-10 hours. So at this point, you should at the very least know how to create an adjustment layer, how to reduce the opacity of an adjustment layer, how to apply a layer mask, as well as inverting the mask, a basic knowledge of the different blending modes, and of some basic retouching tools like the laso tool and clone stamp.
From here there are 2 popular methods of retouch that high end retouchers use. One is dodge and burn, and the other is Frequency Separation. The most popular is Frequency Separation, which is a process in photoshop where you split your image into just the texture on one layer and just the color on another layer, which allows you to make adjustments to just the color or just the texture without affecting the other as happens with using the healing brush. Sounds complicated right? So maybe dodge and burn might be more up your thing. Dodge and Burn requires you to create 2 copies of your image on top of each other and using layer masking. Once layer is a darker image and the other is a brighter image with the layer masks inverted on both. Then zoomed in close to the pixel level you brighten or darken areas so the skin blends together and smooths out, while keeping all the texture intact. Dodge and Burn retouching can often times take 30 minutes or longer to complete a single image.
One does not just jump into being an expert retoucher just because they can set up frequency separation or because they can set up dodge and burn. The skill itself to see what needs to be retouched and developing the skill and often times restraint to do it well can take another 100+ hours of practice. So for those doing the math, you are looking at about 130+ hours to develop the skill in order to become good at retouching. So to answer the question again. Yes we can teach it, but are you dedicated enough to learn?