I am just trying to find a setting that will allow me to paint with gradually darkening effects over each pass, while holding the mouse button down, and not having to keep clicking to increase the opacity/strength. Blender 3D calls this mode "accumulative strokes" I believe. Id like to lighten darkened areas and be able to evenly blend the strokes with the dodge/burn tool, starting with a very low strength and working its way higher. Thanks!
Yes, this is the "Incremental" option in the paintbrush. The effect is visible only if the opacity is low enough (around 20% below) and if the brush spacing is not too tight:
I found it, the "incremental" setting in the brush options, not through the burn/dodge tool, but the paintbrush's options, with the dodge mode selected. Now I'll have to play around with this to get it perfect. I hope this helps other newbies.
Some other things to try:
Any of the brush tools with a reduced opacity or try a mode like linear burn
https://i.imgur.com/Rho5BpJ.jpg
Try the my-paint brushes, digital knife for painting but some good tools for blending.
https://i.imgur.com/NlBKvZ2.jpg
The Gimp 2.10 smudge tool will paint, if the flow is set above zero. Might be useful in some cases.
https://i.imgur.com/fqLpw4y.jpg
The dodge / burn tool does as described by default, lightens/darkens more with subsequent passes, at least it does here.