Gimp paintbrush blendmodes usage

Question

While I can understand singularly every blend mode of the paintbrush from the math point of view, I cannot find a use for most of them (the only ones I used are for drawing a castle and these were "Color,Value,Saturation").

So I'd like to know how do you use/used blend modes (of the paintbrush! I'm NOT interested in blending layers) to paint your pictures in GIMP.

Please avoid "this take 50% of the color from channel blah" answers (I understand the math).

I'd like answers that are (possibily short) sentences that explain the goal and why that blend mode was right for that task. If it is also possible showing a small piece of image before and after application of the paintbrush and the shape of the paintbrush that would be an additional point!

(Photoshop answers counts as long as the same blending mode exist in GIMP, I'll check everything and if works the same.).

I start:

Saturation: I wanted to grey-en certain parts of the image, the saturation mode allowed to do that. This is cool if you exagerate with color, or if you want to make more vivid certain part of the images by increasing the saturation.

Value: I wanted to brighten-darken certain parts of the image to adjust highlights or shadows.

Thanks.

EDIT: To be more precise, I don't want answers like "Pencil is used to change color of pixels along a path to foreground color in selected layer". If the answer end up in saying "this math operation is applied to pixels" than it is usefull to noone and anyway would just be a copy of what GIMP documentation already says.

A more usefull answer is "Pencil is used to draw lines".

Answer 1

First, I use Krita on my works, but blend modes are essentialy the same thing, math operations, maybe somes I will talk here exist only in Krita, but as there is no answer, here it goes:

Addition I use it to create intense specular light effects and glowing areas.

Color dodge it did not "flare" as addition but in contrast it produce much more saturated light, it is good for "neon" light effects. Color dodge may be better than linear dodge, as linear dodge damage a lot dark areas and we are very sensitive to small variations in darker tones.

Overlay I use it to boost contrast and make colors more vivid, it can ruin the image so I'm careful with it because it can ruin the work oversaturating it, it can be used to add patterns too, making the pattern layer work in overlay mode.

Lighten I use it to build fog levels based on darker distant areas as it lighten only areas that are darker than the brush color

greater I use it in help to paint transparent glasses,dresses,etc. It is helpful to paint transparently uniform area because it did not allow the layer to surpass brush transparency, so multiple strokes don't overlay.

multiply simplified shadows, dark patterns. I recommend not abusing it, "shadows have their own color, are not only light based"

soft light soft sun light casting from windows, soft light casts...

I would like to add that programs like Krita have a ridiculous huge list of blend modes, but a small number are really useful. Keeping it simple, in my view, is the best approach in digital painting, it is as simple as traditional, you don't need dozens of brushes and blending modes, the majority have a reduced use and abusing this can result in weird results, so my advise is, paint as a traditional artist (mix colors with brushes) and minimally complement with special brushes and blend modes to avoid weird results and mechanical/stamp strokes. I point it because many people may read it, and generally come to digital expecting the computer to "compose" their work for them. Not to point digital painting has it's own problems.

screen, addition, linear dodge, divide, color dodge are not "light brushes" it will look weird if used everywhere.

burn, darker, subtract multiply are not "shadow brushes", it will look weird if used everywhere.

color + black and white (value) painting is not the same as painting yourself with colors, it will look "grayish" and in lack of contrast, you can mitigate it using overlay and color dodge but using brush with normal colors will produce different results.