Now it's time to prepare your normal maps, and masks for the dynamic wrinkle system. After baking the normals import them to 2D software of your choice, mine is Photoshop. Create two layers and fill one of them with 1 in the green channel, and second with 1 in the red channel. We will use them to create masks.
Now it's important to paint out particular shape keys from your expressions. So here we have anger, here we will have two masks, for frown_mouth, and brow_drop. Paint one of the sides with one of the color, and second with others. Important thing is to stick with colors previously chosen. So if you choose red for the right side and green for the left side, stick with it for all the masks.
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Now I'd hidden one of the shape keys under the black layer, and exported the brows one. Remember to keep the proper naming convention!
These maps don't have to be 4k or 8k or anything high like this, 1k maps will do the job as well. Now repeat the process for every normal map. In some cases, you may reuse maps, or create more versatile ones. Like one for all the brows shape keys, one for all the mouth, one for nose etc. But I'll show the process for all the maps.
Now there's one thing you have to do if you want to shade your character in Eevee. It has a limit of image textures you can use in your material. After connecting to many of them, your model can get pink.
So if you have more than probably something around 15 maps, you should follow this step. Eevee has a count limitation but to the size of the images. So if your maps are 1k, you can create a 2k map, which will fit 4 of 1k maps. And accordingly, if you have 4k maps, you can create an 8k map and fit four of the maps in this one 8k texture. Thanks to that, you'll bypass the limitation.
Bear in mind, that it's important to fit the maps perfectly into the canvas. You don't have to do the same with masks, but you can if you want, this would give you more optimization.
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