I bought a 500 sheet box of velox a while back,so I've been doing a little homework--- I ran across this quick and dirty mask which I.ve used a few times with some success...

79. By tissue papering the printing frame and applying dry yellow ochre to the tissue paper, over the shadow portions of the negative, thus holding them back while the highlights are printing. Or, the glass side of the negative may be ground-glassed and the same application of yellow ochre applied. The former is the more simple, requiring less time. By this method small parts may be held back with the ochre applied to the tissue paper. A negative like this can then be printed evenly by any light; but under circumstances where dodging is employed, you must print further from the light; thus giving more even diffusion and avoiding lines or marks caused by the ochre applied to the tissue paper.

The longer traditional method follows this one---I'll have go back and get the link,I'm on one of these notebook things---one page at a time.