From my recent practice on Marc Brunet’s greyscale to color using gradient map (Check his youtube channel in you’re interested).
In some way this was kinda a mess for me. I know for process like this you have to plan ahead, and I never plan ahead and keep changing stuff even if it is not much. Changing stuff breaks the sketch and shading so I merge both for ease of fixing stuff. But gradient map breaks existing value so the clean sketch need to be in separate layer to keep it safe but mine is not… Tl;dr lots of mistakes happen, check the timelapse if you’re interested.
Krita Timelapse,