I use the cheapest cooking oil in the store. We first apply the pastels or
oil pastel, working light to dark. Dip a finger in a little oil and
blend--again light to dark. Keep wiping the fingers so they don't dirty the
color. I put papers underneath the "painting." Some kids are way too
generous with the oil, but it does dry out overnight. Apply a thin layer of
acrylic varnish. Allow to dry thoroughly if you want to add a second coat.
The results are spectacular.