A couple methods
One great way to clean your pastels is with a feather duster! Ninety-nine cents from Walmart gets you this lovely blue thing that is perfect for quickly getting your sticks back in shape. Use a mask!
For a more thorough job, I use a tuperware container filled with cornmeal, which I feel works a little better than rice. I made the wire mesh tray out of material from the hardware store. I change the cornmeal, once in a great while when it gets really grimmy.
Toning Wallis Sanded Paper
A nice way to get rid of the white
I love Wallis paper, but I don't like to paint on white paper. So, I'll either do an under-painting either in watercolor or with fluid acrylics OR I'll tone the paper as I'm showing in this video. Viscocity is everything here!
Scaling a Thumbnail Sketch
Getting your proportion right
Here's a quick method of getting your proportion right without needing any tools other than a piece of paper and a pastel.