This is not a "how to draw and do cool shit" thing
I USE PAINT TOOL SAI Please feel free to ask questions in the comments, I'm not the best at explaining things because I do them a bit mindlessly, but I TRY HARD. Again, I'd like the remind that this is my own methods and this isnt like.... this isnt the only way to do things, and all the stuff I say is pretty much my opinion haha. I also toss terms around randomly and probably use them wrong.
I have also kept track of the time it took me in case anyone is interested. The TIME at the end of each part summarzies the time taken for that individual part, and not the time taken since the beginning (you would have to add them up for that). I hope you enjoy!
III - REPAINTING
Three layers - the full image layer, hidden and untouched + full image layer being repainted on + hidden green lineart layer.
Tools - Various tools like airbrush or pen or things like that like.. the setting doesnt matter, or the tool type doesnt matter. Airbrush's settings are cosntantly changed on my part, notably opacity wise - as for the pen, I dont really care what tool I'm using for this aslong as it is leaving marks on the canvas. So dont fret over what tool to use and the like cause like really, it doesnt actually have that much difference whether you use 20% opacity or 40% if you know what you're doing / adapt it to the situation.