psiciliano said:When painting with real paint, an artist will dab a brush in paint and then apply it to the canvas. The artist would not reload a brush with paint after every brush stroke – he/she would work the paint already on the brush to draw/render, or shade.
Many alla prima painters would disagree with you. The only time I don't reload an oil brush is if I scumble in a background with a bright or make a sketch. Otherwise every stroke starts out at my palette with fresh paint.
psiciliano said:The result is that I end up continually darkening an area past its intended value.
This happen in real life too, if you glaze layer over layer, it darkens because the transparent layer gets thicker and the light bounces more and more in the substrate, each time it hits a pigment particle in the vehicle / binder, it loses light. The thicker it gets, the more pigment particles it hits and the more light gets removed.
It's the same as how colored glass works, the thicker it is, the less light it lets through.
When you glaze, each consecutive layer darkens your work. The only way to lighten it, is to add opaque paint, since opaque paint reflects light instead of trapping it (which is why white paint is always opaque and why people who use watercolor, transparent paint, use their paper to represent white, or use gouache).
Painter accurately mimmicks this. If you take a glazing oil brush in Painter, you can not make the color lighter, adding a lighter color actually does nothing. The only way to lighten an area is to pick alla prima brushes, that use opaque paint.
Since scumbling is simply the canvas grain pulling off dry paint. All you need to recreate it is set a brush at low wetness, change grain until you see it is picking up the paper texture, and use low opacity.
I don't scumble that much in real life, it's nice for skies, or light shining through trees, but it requires an already dry background, and with oils it's not very productive, in acrylics it's nice for clouds and shades.
There are some brushes that do exhaust their supply of paint...not after a given number of brush stokes, but if you keep your stylus down on the tablet and paint, the brush can be made to run out of Paint. There are certain default brushes that do this normally. And those brushes have a setting called dirty mode, which doesn't refresh the paint from the color panel, but with each brush stroke you paint with the mixed color on the canvas. It is much easier to show in a video, so I did one that I hope will help.