Darkroom 2 Lustrum Press copyright 1978 has a great article by Emmet Gowin on Contour masking..
So an interesting question to ask ourselves: if one is printing on VC paper, does local flashing do anything different than burning with a low contrast filter?
In my work Yes. by doing a pre flash and stopping just at the point of density being seen, I have found the effort far out weighs trying to burn with a low filter. The effect once balanced out is immediate and very predictable.
With this method I am consistently sure of getting tonal separation between the easel arms and white sky, and or snow that is at the edge of the scene.
I absolutely hate blank white areas and maybe its cheating but when the print is viewed in Matt and Frame, the eye is not telling our brains- Hey look at the grey sky, we make it believable, One can get away with quite of bit of flash thanks to this little aspect of visual trickery.