I guess the easiest, fastest painting to do, that lot of people will like, is a pastel on black paper.

   It's the high contrast that makes it look good, not necessarily the craftsmanship.  Remember this rule of thumb.  Leave 20 percent of the colored background paper showing.  Spray it lightly when you're finished, then touch up the highlights and leave it alone.  Leave an eighth inch of air space between the picture and the glass protection.

Degas used a milk casein spray on his pastels that is now available in 2010, by SpectraFix. The colors stay bright, it can also be used over water colors. Use the spray very lightly, you don't want to buckle the paper. Today I use a masonite board primed with pastel grit gesso. It could also be a clear plastic spray on watercolors or the water/alcohol based casine.