When travelling by car, keep a margarine tub filled with small bits of
pastel in cornmeal with you. You can do quick sketches along the way when the
moment hits. The cornmeal keeps the pastels clean and safe. As an
alternative, use rice.
A cigar box makes a good sized container to hold your essential pastel colours. Begin by placing a layer of 1" foam in the bottom to make a soft bed for the sticks. Next, cut a smaller piece of 1" foam to glue on the inside of the lid. This allows the lid to shut tight. Finally, bind the box with a strong elastic.
What about paper you say? Well, cut the number of pieces you'll need, making sure they're all the right size to fit in your pack. Then, cut two pieces of foam core the same size as the pastel paper. Place the paper in-between the foam core covers and bind it with elastic. Include 4 small builldog clips as well. When you stop to work place a piece of paper on top of the foam core and secure it with the clips. When you want to start a new work, place the finished one at the bottom of your paper pile inside the foam core covers and secure. The secret is not to let the papers shift and smudge the pastel. you can use only one piece of foam core as long as the stack of pastel paper is wrong side up until you need a piece.
Finally, don't forget a small air cushion to keep your other 'assets' protected from the damp while working and wet naps for cleaning up.