don't know if this will help, but for Raith of the FHCO we use 2 layers in Photoshop, bottom one black, top one white. He sketches in the shape of his mt chains in black on the white layer, and then uses one of the natural brushes in PS to erase the white from the white layer where he wants black. A pic is below. Don't know if this way is any better than just applying black to the white, but he gets better results this way. Don't know either if you can erase with vectors/whatever in this manner in ikscape.
SeerBlue and Raith Eliathy