Many crayon artists (you can find a few online) use solvents to soften their appearance. It can be a wonderful look but, personally, I love the pixilated look the crayon creates when applied just as is. Look at the art examples in this post _ you can see the speckled look crayon has when applied in layers. This adds to the realism, especially when creating an out_of_focus background, such as in these two images.
This art therapy trend has yet to hit America, but because publishers have found it immensely profitable, it's probably only a matter of time before you find yourself shopping for a new box of crayons. And hey, why not? Coloring is a fun and joyful activity that is a much easier way to reduce stress than, say, dragging yourself to the gym. It just might get awkward if your friends find your completely finished Benedict Cumberbatch coloring book.