The drawing had been previously sprayed with fixative, so all I had to do was take a large piece of illustration board, and carefully glue the somewhat fragile drawing to the heavier board. I used a mixture of white glue and matte medium and was careful to avoid "ripples" in the paper. In fact, when I let it dry overnight, the whole thing tightened up nicely.
I used water soluble crayons to draw my landscape (based on a previous painting) and decided I would try to retain some of the charcoal drawing underneath, and cover other parts with opaque acrylics. It took many layers and a lot of LOOKING to balance the greens with the black/cream-colored sections. Some of the black lines are very stubborn and hard to cover up, so I left them as is. I enjoyed this intuitive way of painting and hope to do more paintings in this style---all I need are some charcoal drawings!